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/slab/floorplan-affordances.ts

@@ -37,6 +37,7 @@ const slabSnapOptions = {
       excludeId: node.id,
       nodes: sceneNodes,
       altKey: modifiers.altKey,
+      shiftKey: modifiers.shiftKey,
     }).point
   },
 }