egui takes i.modifiers from ModifiersChanged events, not from the modifiers
on a pointer event, so a control-channel Shift-click arrived as a plain click
(e.g. Shift-click in the Timeline replaced the selection instead of adding).
ui.click and ui.drag now queue ModifiersChanged before the gesture and clear
it after. The synthetic-input feeding moves into EffectcraftApp::feed_synthetic
so it can be tested; the new tests fail without the fix.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
