fix(editor): wall-item placement & floorplan polish

Polish pass on the placement/interaction overhaul. Five fixes:

- Item-on-item rotation box: the cursor box held the host-local yaw instead of
  world yaw, so it diverged from the item by the host's rotation when stacked on
  another item (fine on the floor). The box now derives world yaw from the
  mesh/host quaternion in both the R/T handler and the move-start sync.

- 2D floorplan move now respects the snapping mode (parity with 3D): grid
  quantization only in grid mode, alignment guides only in lines/magnetic mode;
  Shift/Alt no longer hard-bypass. Item move also plays the move "tick" SFX on
  any resolved-position change, like the 3D move.

- Wall-side item footprint side: the 2D footprint depth offset extended toward the
  wall (centerLocalZ -depth/2) instead of into the room, mirroring the item across
  the wall; flipped to +depth/2. Aligned the undefined-side anchor to the 3D
  convention (front +1 / else -1).

- 3D placement preview side: the wall-side preview bounds + base plane used a -Z
  (into-wall) convention; flipped to +Z (into-room) to match the body and the
  fixed 2D footprint. The 2D live preview during a 3D wall placement now publishes
  the plan rotation (wall angle + item yaw) instead of the world cursor yaw, which
  was pi off on a wall face and flipped the footprint to the far side.

- Cmd/Ctrl+R no longer rotates/flips the selected node (it reaches the browser
  reload); guard added to the global selected-node handler and the 2D move overlay.

Verified: core/editor/nodes tsc, biome, editor 162/0 + nodes 292/0 tests.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/nodes/src/item/floorplan.ts

@@ -67,7 +67,7 @@ function resolveItemTransform(
     const wallRotation = -Math.atan2(wall.end[1] - wall.start[1], wall.end[0] - wall.start[0])
     const wallLocalZ =
       item.asset.attachTo === 'wall-side'
-        ? ((wall.thickness ?? 0.1) / 2) * (item.side === 'back' ? -1 : 1)
+        ? ((wall.thickness ?? 0.1) / 2) * (item.side === 'front' ? 1 : -1)
         : item.position[2]
     const [offsetX, offsetY] = rotateVec(item.position[0], wallLocalZ, wallRotation)
     result = {
@@ -160,9 +160,12 @@ export function buildItemFloorplan(node: ItemNode, ctx: GeometryContext): Floorp
   const [width, , depth] = getScaledDimensions(node)
   if (width <= 0 || depth <= 0) return null
 
-  // Wall-side items are anchored at the front face — center their footprint
-  // half-a-depth back toward the wall surface.
-  const centerLocalZ = node.asset.attachTo === 'wall-side' ? -depth / 2 : 0
+  // Wall-side items are anchored at the mounted wall face; their body extends
+  // depth-ward AWAY from the wall (into the room), so push the footprint centre
+  // a half-depth out along the item's local +Z. After the front/back π flip in
+  // `transform.rotation`, +depth/2 always points off the wall for either side;
+  // a negative offset would lay the footprint across the wall onto the far side.
+  const centerLocalZ = node.asset.attachTo === 'wall-side' ? depth / 2 : 0
   const [centerOffsetX, centerOffsetY] = rotateVec(0, centerLocalZ, transform.rotation)
   const cx = transform.x + centerOffsetX
   const cy = transform.y + centerOffsetY