Batch held arrow-key transforms into a single undo entry and autosave

[davidsteinmeyer]

Summary

Keyboard movement committed a history snapshot and synced the project on every keydown repeat, so holding an arrow key produced one undo entry and one autosave per repeat. This reuses the existing pointer-drag interaction model so a continuous hold is one undo step and one autosave, while discrete taps still record individually. Geometry, selection, and durability are unchanged.

Root cause

• nudgeSelected and raiseSelected called commitShapes on every keydown, which appended a history snapshot and called syncProjectShapes.
• Pointer drags already batch via projectInteractionActive / finalizeInteractionHistory, but keyboard movement bypassed that path.

Changes

• Added heldMoveKeysRef and keyboardInteractionOwnedRef to track the keys in a hold.
• Added applyLiveShapes, the interaction-time counterpart of commitShapes: it updates shapes and marks the interaction as changed without appending history or syncing.
• nudgeSelected/raiseSelected now read shapesRef.current and use applyLiveShapes while an interaction is active, falling back to commitShapes otherwise.
• Keydown starts an interaction on the first movement key (updateProjectInteractionActive(true)), and keyup finalizes it when the last held movement key is released. blur and visibilitychange (hidden) also finalize so a missed keyup cannot wedge the interaction.
• The thumbnail effect no longer fingerprints the whole scene during an active interaction; it defers to the post-interaction run.

Testing

• npm run typecheck
• Manually tested the affected workflow