Root-caused via temporary logcat tracing (touch events, DragArbiter state,
Selection::drag dispatch), reproduced against a real sandbox session: a
gesture's ACTION_DOWN can land on a row's own padding/gap or its header,
which CursorSense has no sensor over, so the widget that ends up handling
the gesture only ever sees Pressing frames and DragArbiter never gets
press_start -- leaving it stuck in Idle (answers Undecided forever) for the
rest of that gesture. Not the previously-suspected coalesced first
ACTION_MOVE, which is now ruled out.
DragArbiter::is_idle() lets Selection::drag notice a Pressing frame with
no matching press_start and recover the press there instead. Four new unit
tests, one of which fails on the pre-fix code.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>