Phase 5 Stage D moves: align useLiveTransforms with the direct mesh.position delta

User reported the slab/fence mesh jittered/teleported continuously
while dragging (not on commit — during the drag). Root cause: the
move tool wrote TWO conflicting values per grid:move tick:

 1. `mesh.position.set(deltaX, 0, deltaZ)` — relative offset, direct
    Three.js mutation.
 2. `useLiveTransforms.set(id, { position: [originalCenter + deltaX,
    0, originalCenter + deltaZ], rotation: 0 })` — absolute world
    position of the translated polygon center.

`ParametricNodeRenderer` reads `useLiveTransforms` and binds it via
React: `<group position={liveTransform.position}>`. So every Zustand
notification re-rendered the renderer and reconciled the group's
position back to "originalCenter + delta" (the absolute), overriding
the "delta" the direct mutation had just written. The two systems
fought every frame → visible jitter.

Fix: `useLiveTransforms.position` now holds the SAME delta the direct
mutation uses (`[deltaX, 0, deltaZ]`). React reconciles to the same
value the direct mutation already set — no conflict.

The cursor sphere position stays as the translated polygon center
(it's tracked separately via React state, not `useLiveTransforms`).

Ceiling aligned for consistency, though CeilingRenderer doesn't read
`useLiveTransforms` so the value there has no rendering effect.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/nodes/src/ceiling/move-tool.tsx

@@ -90,8 +90,12 @@ export const MoveCeilingTool: React.FC<{ node: CeilingNode }> = ({ node }) => {
     const applyPreview = (deltaX: number, deltaZ: number) => {
       deltaRef.current = [deltaX, deltaZ]
       setMeshOffset(ceilingId as AnyNodeId, deltaX, deltaZ, height)
+      // Aligned with slab/fence: the delta matches the direct mesh
+      // mutation. CeilingRenderer doesn't bind position via React, so
+      // this entry isn't consumed for rendering, but kept consistent
+      // in case other systems read it.
       useLiveTransforms.getState().set(ceilingId, {
-        position: [originalCenter[0] + deltaX, height, originalCenter[1] + deltaZ],
+        position: [deltaX, 0, deltaZ],
         rotation: 0,
       })
       setCursorLocalPos([originalCenter[0] + deltaX, height, originalCenter[1] + deltaZ])

packages/nodes/src/fence/move-tool.tsx

@@ -104,17 +104,14 @@ function setMeshOffset(fenceId: FenceNode['id'], deltaX: number, deltaZ: number)
   if (mesh) mesh.position.set(deltaX, 0, deltaZ)
 }
 
-function setFenceLiveTransform(
-  fenceId: FenceNode['id'],
-  start: [number, number],
-  end: [number, number],
-  deltaX: number,
-  deltaZ: number,
-): void {
-  const cx = (start[0] + end[0]) / 2
-  const cz = (start[1] + end[1]) / 2
+function setFenceLiveTransform(fenceId: FenceNode['id'], deltaX: number, deltaZ: number): void {
+  // useLiveTransforms holds the SAME delta the direct mesh.position
+  // mutation uses — ParametricNodeRenderer reads it and reconciles
+  // `<group position={liveTransform.position}>` via React. Mismatched
+  // values here cause the two systems to fight per frame (jitter
+  // during drag).
   useLiveTransforms.getState().set(fenceId, {
-    position: [cx + deltaX, 0, cz + deltaZ],
+    position: [deltaX, 0, deltaZ],
     rotation: 0,
   })
 }
@@ -168,10 +165,10 @@ export const MoveFenceTool: React.FC<{ node: FenceNode }> = ({ node }) => {
     const applyPreview = (deltaX: number, deltaZ: number) => {
       deltaRef.current = [deltaX, deltaZ]
       setMeshOffset(fenceId, deltaX, deltaZ)
-      setFenceLiveTransform(fenceId, originalStart, originalEnd, deltaX, deltaZ)
+      setFenceLiveTransform(fenceId, deltaX, deltaZ)
       for (const linked of linkedOriginals) {
         setMeshOffset(linked.id, deltaX, deltaZ)
-        setFenceLiveTransform(linked.id, linked.start, linked.end, deltaX, deltaZ)
+        setFenceLiveTransform(linked.id, deltaX, deltaZ)
       }
       // Cursor at translated polygon center.
       const centerX = (originalStart[0] + originalEnd[0]) / 2

packages/nodes/src/slab/move-tool.tsx

@@ -109,11 +109,17 @@ export const MoveSlabTool: React.FC<{ node: SlabNode }> = ({ node }) => {
       // Visual: translate the slab MESH only. No scene mutation, no
       // polygon rebuild, no React re-render of geometry.
       setMeshOffset(slabId as AnyNodeId, deltaX, deltaZ)
+      // useLiveTransforms holds the same delta the direct mesh.position
+      // mutation uses — ParametricNodeRenderer reads it and reconciles
+      // `<group position={liveTransform.position}>` via React. Mismatched
+      // values here cause the two systems to fight per frame (jitter
+      // during drag).
       useLiveTransforms.getState().set(slabId, {
-        position: [originalCenter[0] + deltaX, 0, originalCenter[1] + deltaZ],
+        position: [deltaX, 0, deltaZ],
         rotation: 0,
       })
-      // Cursor sphere follows the new polygon center.
+      // Cursor sphere follows the new polygon center (independent of
+      // group position).
       setCursorLocalPos([originalCenter[0] + deltaX, 0, originalCenter[1] + deltaZ])
     }