A stylus pass through a committed stroke in eraser mode fires onEraseStroke for
it; a pass far from any stroke erases nothing. Locks in the eraser path (the
user reported eraser reliability issues) as a regression guard without a device.
flutter analyze lib/editor clean; 237/237 tests (+2).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
