The scroll offset semantics were inverted for the wheel and PageUp:
is the content offset (larger = newer), so scrolling up must DECREASE it, but
ScrollUp and PageUp both INCREASED it — every wheel event (either direction)
moved toward the bottom, and at the bottom (follow=true) an up-notch added 3
then got clamped back to max, making the wheel dead until keyboard-scrolling
away. Now:
- wheel ScrollUp/ScrollLeft: offset -1, follow cleared (works from the bottom)
- wheel ScrollDown/ScrollRight: offset +1, follow restored at the bottom
- PageUp: offset - view_height; PageDown: offset + view_height
- one line per wheel notch (was 3) for line-by-line scrolling
regression test drives handle_mouse with synthetic events (direction,
line-step, no underflow, follow transitions).
acddf7be1b