feat(tui): cross-platform wheel scroll and two-level expansion

1. wheel: scrolling up now clears follow (the real bug — with follow=true every
   draw snapped back to the bottom, so the wheel appeared dead on both Linux
   and Windows); crossterm already normalizes xterm (Linux) and ConPTY
   (Windows) wheel events to ScrollUp/ScrollDown, and ScrollLeft/ScrollRight
   are handled too
2. expansion becomes three-state (collapsed → partial → full → collapsed):
   the first expand shows the first 20 lines with a '… 还有 N 行（再次点击/Tab
   展开全部）' hint; the second expand reveals everything. Applies to thinking,
   tool-execution output and tool-result content. ToolCall args stay
   single-level human-readable.

tests: three-state cycle, full-flag propagation

crates/focus-tui/src/app.rs

@@ -199,6 +199,9 @@ pub struct App {
     /// Committed tool_result execution durations ((message idx, 0) → ms).
     pub tool_durations: HashMap<(usize, usize), u64>,
     pub expanded: HashSet<BlockId>,
+    /// 二级展开（显示全部内容）的块。
+    /// Blocks expanded to the full level (show everything).
+    pub full: HashSet<BlockId>,
     pub notes: Vec<String>,
     pub status: String,
     pub scroll: u16,
@@ -237,6 +240,7 @@ impl App {
             thinking_durations: HashMap::new(),
             tool_durations: HashMap::new(),
             expanded: HashSet::new(),
+            full: HashSet::new(),
             notes: Vec::new(),
             status: String::new(),
             scroll: 0,
@@ -552,6 +556,7 @@ impl App {
         self.thinking_durations.clear();
         self.tool_durations.clear();
         self.expanded.clear();
+        self.full.clear();
         self.last_usage = None;
         self.notes.clear();
         self.push_note("新会话已开始。");
@@ -577,6 +582,7 @@ impl App {
         self.thinking_durations.clear();
         self.tool_durations.clear();
         self.expanded.clear();
+        self.full.clear();
         self.notes.clear();
         self.push_note(format!(
             "已加载会话 {}（{} 条消息）。",
@@ -852,14 +858,23 @@ impl App {
                         .iter()
                         .find(|g| g.start <= content_row && content_row < g.end)
                     {
-                        toggle_expanded(&mut self.expanded, &block.id);
+                        cycle_expansion(&mut self.expanded, &mut self.full, &block.id);
                     }
                 }
             }
-            MouseEventKind::ScrollUp => self.scroll = self.scroll.saturating_add(3),
+            // crossterm 把 Linux（xterm 协议）与 Windows（ConPTY）的滚轮事件
-            MouseEventKind::ScrollDown => {
+            // 都归一化为 ScrollUp/ScrollDown；向上滚必须取消 follow，
-                let max = self.max_scroll();
+            // 否则每次绘制会被吸回底部。
-                self.scroll = (self.scroll + 3).min(max);
+            // crossterm normalizes wheel events from both Linux (xterm) and
+            // Windows (ConPTY) to ScrollUp/ScrollDown; scrolling up must clear
+            // follow, otherwise every draw snaps back to the bottom.
+            MouseEventKind::ScrollUp | MouseEventKind::ScrollLeft => {
+                self.follow = false;
+                self.scroll = self.scroll.saturating_add(3);
+            }
+            MouseEventKind::ScrollDown | MouseEventKind::ScrollRight => {
+                self.scroll = (self.scroll + 3).min(self.max_scroll());
+                self.follow = self.scroll >= self.max_scroll();
             }
             _ => {}
         }
@@ -893,7 +908,7 @@ impl App {
             })
             .map(|g| g.id.clone());
         if let Some(id) = id {
-            toggle_expanded(&mut self.expanded, &id);
+            cycle_expansion(&mut self.expanded, &mut self.full, &id);
         }
     }
 

crates/focus-tui/src/state.rs

@@ -58,6 +58,10 @@ pub enum UiBlock {
         duration_ms: Option<u64>,
         tokens: u64,
         expanded: bool,
+        /// 二级展开：true 表示显示全部内容（false 时只显示部分）。
+        /// Second-level expansion: true shows everything (false shows a
+        /// partial preview).
+        full: bool,
     },
     /// assistant 发出的工具调用。
     /// A tool call issued by the assistant.
@@ -77,6 +81,7 @@ pub enum UiBlock {
         is_error: bool,
         duration_ms: Option<u64>,
         expanded: bool,
+        full: bool,
     },
     /// 运行错误（assistant 消息的 error_message，红色显示）。
     /// A run error (an assistant message's error_message, shown in red).
@@ -93,6 +98,7 @@ pub enum UiBlock {
         result_text: String,
         is_error: bool,
         expanded: bool,
+        full: bool,
     },
     /// 系统提示（欢迎、帮助、状态说明等）。
     /// A system note (welcome, help, status).
@@ -367,6 +373,7 @@ pub fn build_blocks(
     tool_durations: &std::collections::HashMap<(usize, usize), u64>,
     run_state: Option<&RunState>,
     expanded: &HashSet<BlockId>,
+    full: &HashSet<BlockId>,
 ) -> Vec<UiBlock> {
     let mut out = Vec::new();
     for (mi, msg) in transcript.iter().enumerate() {
@@ -392,6 +399,7 @@ pub fn build_blocks(
                         block,
                         thinking_durations.get(&(mi, bi)).copied(),
                         expanded,
+                        full,
                     );
                 }
                 // 具体错误文本（如 provider 的 HTTP 400 详情）。
@@ -404,13 +412,15 @@ pub fn build_blocks(
                 }
             }
             Message::ToolResult(t) => {
+                let id = BlockId(format!("m{}-r", mi));
                 out.push(UiBlock::ToolResult {
-                    id: BlockId(format!("m{}-r", mi)),
+                    id: id.clone(),
                     name: t.tool_name.clone(),
                     text: join_text(&t.content),
                     is_error: t.is_error,
                     duration_ms: tool_durations.get(&(mi, 0)).copied(),
-                    expanded: expanded.contains(&BlockId(format!("m{}-r", mi))),
+                    expanded: expanded.contains(&id),
+                    full: full.contains(&id),
                 });
             }
         }
@@ -433,6 +443,7 @@ pub fn build_blocks(
                     block,
                     duration,
                     expanded,
+                    full,
                 );
             }
             if let Some(err) = &partial.error_message {
@@ -452,8 +463,9 @@ pub fn build_blocks(
             .enumerate()
             .filter(|(_, e)| e.status == ExecStatus::Running)
         {
+            let id = BlockId(format!("exec-{}", ei));
             out.push(UiBlock::ToolExec {
-                id: BlockId(format!("exec-{}", ei)),
+                id: id.clone(),
                 name: exec.name.clone(),
                 summary: exec.summary.clone(),
                 status: exec.status,
@@ -461,7 +473,8 @@ pub fn build_blocks(
                 output: exec.output.clone(),
                 result_text: exec.result_text.clone(),
                 is_error: exec.is_error,
-                expanded: expanded.contains(&BlockId(format!("exec-{}", ei))),
+                expanded: expanded.contains(&id),
+                full: full.contains(&id),
             });
         }
     }
@@ -477,8 +490,10 @@ fn push_content_block(
     block: &ContentBlock,
     thinking_duration: Option<u64>,
     expanded: &HashSet<BlockId>,
+    full: &HashSet<BlockId>,
 ) {
     let is_expanded = expanded.contains(&id);
+    let is_full = full.contains(&id);
     match block {
         ContentBlock::Text(t) => out.push(UiBlock::Text {
             id,
@@ -490,6 +505,7 @@ fn push_content_block(
             duration_ms: thinking_duration,
             tokens: focus_harness::estimate_tokens(&t.thinking),
             expanded: is_expanded,
+            full: is_full,
         }),
         ContentBlock::ToolCall(tc) => out.push(UiBlock::ToolCall {
             id,
@@ -502,8 +518,20 @@ fn push_content_block(
     }
 }
 
-/// 切换一个块的展开状态。
+/// 三态展开循环：折叠 → 部分 → 全部 → 折叠。
-/// Toggle a block's expansion state.
+/// Three-state expansion cycle: collapsed → partial → full → collapsed.
+pub fn cycle_expansion(expanded: &mut HashSet<BlockId>, full: &mut HashSet<BlockId>, id: &BlockId) {
+    if full.remove(id) {
+        expanded.remove(id);
+    } else if expanded.remove(id) {
+        full.insert(id.clone());
+    } else {
+        expanded.insert(id.clone());
+    }
+}
+
+/// 切换一个块的展开状态（两态，供单级展开的块使用）。
+/// Toggle a block's expansion (two-state, for single-level blocks).
 pub fn toggle_expanded(expanded: &mut HashSet<BlockId>, id: &BlockId) {
     if !expanded.remove(id) {
         expanded.insert(id.clone());

crates/focus-tui/src/ui.rs

@@ -141,6 +141,7 @@ fn draw_messages(frame: &mut Frame, area: Rect, app: &mut App) {
         &app.tool_durations,
         app.run_state.as_ref(),
         &app.expanded,
+        &app.full,
     ));
 
     let width = area.width.saturating_sub(1).max(1) as usize;
@@ -247,6 +248,7 @@ fn block_lines(block: &UiBlock, width: usize) -> Vec<Line<'static>> {
             duration_ms,
             tokens,
             expanded,
+            full,
             ..
         } => {
             if *expanded {
@@ -254,9 +256,7 @@ fn block_lines(block: &UiBlock, width: usize) -> Vec<Line<'static>> {
                     "▾ 🧠 thinking",
                     Style::new().fg(Color::Yellow).bold(),
                 )));
-                for line in wrap_text(text, width.saturating_sub(2)) {
+                out.extend(preview_lines(text, *full, width, "  ", dim));
-                    out.push(Line::from(Span::styled(format!("  {}", line), dim)));
-                }
                 out.push(Line::from(Span::styled("  ──", dim)));
             } else {
                 let dur = duration_ms
@@ -313,6 +313,7 @@ fn block_lines(block: &UiBlock, width: usize) -> Vec<Line<'static>> {
             is_error,
             duration_ms,
             expanded,
+            full,
             ..
         } => {
             let mark = if *is_error { "✗" } else { "✓" };
@@ -329,9 +330,7 @@ fn block_lines(block: &UiBlock, width: usize) -> Vec<Line<'static>> {
                         Style::new().fg(Color::Green).bold()
                     },
                 )));
-                for line in wrap_text(text, width.saturating_sub(2)) {
+                out.extend(preview_lines(text, *full, width, "  ", dim));
-                    out.push(Line::from(Span::styled(format!("  {}", line), dim)));
-                }
             } else {
                 out.push(Line::from(Span::styled(
                     format!("▸ 📦 {} {}{}（点击/Tab 展开）", mark, name, dur),
@@ -351,6 +350,7 @@ fn block_lines(block: &UiBlock, width: usize) -> Vec<Line<'static>> {
             result_text,
             is_error,
             expanded,
+            full,
             ..
         } => {
             let running = *status == ExecStatus::Running;
@@ -360,24 +360,21 @@ fn block_lines(block: &UiBlock, width: usize) -> Vec<Line<'static>> {
                     format!("▾ 🔧 {} · {}", summary, state),
                     Style::new().fg(Color::Magenta).bold(),
                 )));
-                if running && !output.is_empty() {
+                // 运行中：流式输出实时预览；结束后：结果文本（部分/全部）。
-                    for line in wrap_text(output, width.saturating_sub(2)) {
+                // Running: live streaming preview; done: result text
-                        out.push(Line::from(Span::styled(format!("  {}", line), dim)));
+                // (partial/full).
-                    }
+                let body = if running {
-                }
+                    output.clone()
-                if !running {
+                } else {
-                    if !result_text.is_empty() {
+                    result_text.clone()
-                        for line in wrap_text(result_text, width.saturating_sub(2)) {
+                };
-                            out.push(Line::from(Span::styled(format!("  {}", line), dim)));
+                out.extend(preview_lines(&body, *full, width, "  ", dim));
-                        }
+                if !running && *is_error {
-                    }
-                    if *is_error {
                     out.push(Line::from(Span::styled(
                         "  ✗ 工具执行失败",
                         Style::new().fg(Color::Red),
                     )));
                 }
-                }
             } else {
                 let dur = duration_ms
                     .map(format_duration)
@@ -670,3 +667,45 @@ fn md_line_to_ratatui(md: &MdLine) -> Line<'static> {
         .collect();
     Line::from(spans)
 }
+
+/// 展开时的内容预览：`full` 时显示全部，否则只显示前若干行并提示剩余行数。
+/// Content preview when expanded: `full` shows everything, otherwise the first
+/// few lines plus a remaining-line-count hint.
+fn preview_lines(
+    text: &str,
+    full: bool,
+    width: usize,
+    indent: &str,
+    style: Style,
+) -> Vec<Line<'static>> {
+    /// 部分预览的最大行数。
+    /// Max lines shown in a partial preview.
+    const PARTIAL_MAX_LINES: usize = 20;
+    let total = text.lines().count();
+    let lines: Vec<&str> = text.lines().collect();
+    let shown: Vec<&str> = if full || total <= PARTIAL_MAX_LINES {
+        lines
+    } else {
+        lines.iter().take(PARTIAL_MAX_LINES).copied().collect()
+    };
+    let mut out: Vec<Line<'static>> = Vec::new();
+    for line in shown {
+        for wrapped in wrap_text(line, width.saturating_sub(2)) {
+            out.push(Line::from(Span::styled(
+                format!("{}{}", indent, wrapped),
+                style,
+            )));
+        }
+    }
+    if !full && total > PARTIAL_MAX_LINES {
+        out.push(Line::from(Span::styled(
+            format!(
+                "{}… 还有 {} 行（再次点击/Tab 展开全部）",
+                indent,
+                total - PARTIAL_MAX_LINES
+            ),
+            style,
+        )));
+    }
+    out
+}

crates/focus-tui/tests/state_tests.rs

@@ -157,6 +157,7 @@ fn blocks_are_collapsed_by_default_and_summarized() {
         &HashMap::new(),
         None,
         &expanded,
+        &HashSet::new(),
     );
 
     // 折叠态：思考块只显示摘要（无展开文本），工具调用只显示摘要。
@@ -197,6 +198,7 @@ fn blocks_are_collapsed_by_default_and_summarized() {
         &HashMap::new(),
         None,
         &expanded,
+        &HashSet::new(),
     );
     let mut expanded_count = 0;
     for b in &blocks {
@@ -230,6 +232,7 @@ fn build_blocks_includes_live_run() {
         &HashMap::new(),
         Some(&rs),
         &HashSet::new(),
+        &HashSet::new(),
     );
     // live 头 + 思考 + 文本。
     // live header + thinking + text.
@@ -316,6 +319,7 @@ fn error_message_renders_as_error_block() {
         &HashMap::new(),
         None,
         &HashSet::new(),
+        &HashSet::new(),
     );
     let err = blocks
         .iter()
@@ -362,6 +366,7 @@ fn tool_duration_shows_in_tool_result_block() {
         &durations,
         None,
         &HashSet::new(),
+        &HashSet::new(),
     );
     let tr = blocks.iter().find_map(|b| match b {
         UiBlock::ToolResult { duration_ms, .. } => Some(*duration_ms),
@@ -398,6 +403,7 @@ fn live_renders_only_running_execs() {
         &HashMap::new(),
         Some(&rs),
         &HashSet::new(),
+        &HashSet::new(),
     );
     assert!(
         !blocks.iter().any(|b| matches!(b, UiBlock::ToolExec { .. })),
@@ -419,6 +425,7 @@ fn live_renders_only_running_execs() {
         &HashMap::new(),
         Some(&rs),
         &HashSet::new(),
+        &HashSet::new(),
     );
     assert!(
         blocks.iter().any(|b| matches!(
@@ -431,3 +438,62 @@ fn live_renders_only_running_execs() {
         "running exec must render"
     );
 }
+
+/// 三态展开循环：折叠 → 部分 → 全部 → 折叠。
+/// Three-state expansion cycle: collapsed → partial → full → collapsed.
+#[test]
+fn expansion_cycles_three_states() {
+    let id = BlockId("live-0".into());
+    let mut expanded = HashSet::new();
+    let mut full = HashSet::new();
+
+    // 折叠 → 部分。
+    // Collapsed → partial.
+    cycle_expansion(&mut expanded, &mut full, &id);
+    assert!(expanded.contains(&id));
+    assert!(!full.contains(&id));
+
+    // 部分 → 全部。
+    // Partial → full.
+    cycle_expansion(&mut expanded, &mut full, &id);
+    assert!(!expanded.contains(&id));
+    assert!(full.contains(&id));
+
+    // 全部 → 折叠。
+    // Full → collapsed.
+    cycle_expansion(&mut expanded, &mut full, &id);
+    assert!(!expanded.contains(&id));
+    assert!(!full.contains(&id));
+}
+
+/// 二级展开标志进入 ToolResult 块。
+/// The full-level flag reaches ToolResult blocks.
+#[test]
+fn full_flag_reaches_blocks() {
+    let transcript = vec![Message::ToolResult(ToolResultMessage {
+        tool_call_id: "c1".into(),
+        tool_name: "shell".into(),
+        content: vec![ContentBlock::text("out")],
+        details: JsonValue::obj(),
+        is_error: false,
+        timestamp: 0,
+    })];
+    let mut full = HashSet::new();
+    full.insert(BlockId("m0-r".into()));
+    let blocks = build_blocks(
+        &transcript,
+        &HashMap::new(),
+        &HashMap::new(),
+        None,
+        &HashSet::new(),
+        &full,
+    );
+    let tr = blocks
+        .iter()
+        .find_map(|b| match b {
+            UiBlock::ToolResult { full, .. } => Some(*full),
+            _ => None,
+        })
+        .expect("tool result block");
+    assert!(tr, "full flag must propagate");
+}