fix(editor): harden editor interactions and WebGPU rendering

Fix editor bug sweep regressions, WebGPU CSG/material crashes, Shift snap bypass behavior, arrow handle drag projection, and the wall preview null guard covered by the Sentry follow-up PRs.

packages/nodes/src/shelf/floorplan-move.ts

@@ -66,7 +66,7 @@ export const shelfFloorplanMoveTarget: FloorplanMoveTarget<ShelfNode> = ({ node,
       const gridSnapped = resolveCursor(planPoint, { snap }) as WallPlanPoint
       // Figma-style alignment layered on the grid snap — the shelf footprint
       // edges snap to neighbours / wall faces and a guide is published. Alt
-      // bypasses (matches placement tools' "No snap").
+      // bypasses alignment; Shift bypasses all snap.
       const { point: snapped } = applyFloorplanAlignment(
         gridSnapped,
         movingFootprintAnchors(
@@ -76,7 +76,7 @@ export const shelfFloorplanMoveTarget: FloorplanMoveTarget<ShelfNode> = ({ node,
           originalRotationY,
         ),
         candidates,
-        { bypass: modifiers.altKey },
+        { bypass: modifiers.altKey || modifiers.shiftKey },
       )
       const next: [number, number, number] = [snapped[0], originalPosition[1], snapped[1]]
       lastPosition = next
@@ -85,7 +85,7 @@ export const shelfFloorplanMoveTarget: FloorplanMoveTarget<ShelfNode> = ({ node,
       // and the placement coordinators. Item / slab / wall flows fire
       // the same cue, so the shelf following along is the expected UX.
       const snapKey = `${snapped[0]},${snapped[1]}`
-      if (snapKey !== lastSnapKey) {
+      if (!modifiers.shiftKey && snapKey !== lastSnapKey) {
         triggerSFX('sfx:grid-snap')
         lastSnapKey = snapKey
       }

packages/nodes/src/shelf/tool.tsx

@@ -83,7 +83,8 @@ const ShelfTool = () => {
         rawZ: event.localPosition[2],
         gridStep: useEditor.getState().gridSnapStep,
         candidates: alignmentCandidates,
-        bypassAlignment: event.nativeEvent?.altKey === true,
+        bypassAlignment: event.nativeEvent?.altKey === true || event.nativeEvent?.shiftKey === true,
+        bypassGrid: event.nativeEvent?.shiftKey === true,
       })
       useAlignmentGuides.getState().set(guides)
 
@@ -97,7 +98,10 @@ const ShelfTool = () => {
       lastCursorRef.current = position
 
       const prev = previousSnapRef.current
-      if (!prev || prev[0] !== position[0] || prev[1] !== position[2]) {
+      if (
+        event.nativeEvent?.shiftKey !== true &&
+        (!prev || prev[0] !== position[0] || prev[1] !== position[2])
+      ) {
         triggerSFX('sfx:grid-snap')
         previousSnapRef.current = [position[0], position[2]]
       }
@@ -110,7 +114,12 @@ const ShelfTool = () => {
       // first). Both paths apply the same grid snap.
       const position =
         lastCursorRef.current ??
-        getLevelLocalSnappedPosition(activeLevelId, event, useEditor.getState().gridSnapStep)
+        getLevelLocalSnappedPosition(
+          activeLevelId,
+          event,
+          useEditor.getState().gridSnapStep,
+          event.nativeEvent?.shiftKey === true,
+        )
       const shelf = ShelfNode.parse({
         ...shelfDefinition.defaults(),
         name: 'Shelf',