Three user-reported regressions, all in the Stage D move/curve ports:
1. **Fence/wall bend cancelled the fence creation on Ctrl-Z.** The
action.commit's `return false` shortcut on "no offset change"
bypassed the dance entirely — pastStates wasn't touched, so the
next Ctrl-Z fell through to whatever preceded activation
(typically the create step). Fix: always run the dance, even on
no-op commits. First Ctrl-Z then absorbs a silent no-op entry,
subsequent presses roll back real prior actions. Same fix applied
to fence move-endpoint, fence move, slab move, ceiling move.
2. **Slab/ceiling move 'maximum update depth exceeded' loop.** The
`useScene` selector in `SlabMoveTool` returned a freshly-allocated
`[sx, sz]` tuple on every call. Zustand's `Object.is` equality
failed each comparison → re-subscribe → re-render → loop. Fix:
subscribe to the stable live-node reference and derive the center
via `useMemo`. Same recipe for fence/ceiling move-tools, including
memoizing the `originalCenter` fallback that was getting a new
array per render.
3. **No grid-snap sfx during move drag.** Action `preview` now tracks
the last snapped pointer on a mutable `lastSnapped` ctx field and
emits `sfx:grid-snap` when it changes between ticks. Matches the
legacy MoveFenceTool's per-tick sound.
Locking test for foot-gun 1 lives in
`packages/core/src/services/single-undo-dance.test.ts`.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
