Merge origin/main into feat/placement-interaction-overhaul

Resolve 7 conflicts keeping our snapping migration + floorplan perf work as
source of truth, combined with main's MEP run-continuation / Alt-detach /
latch handles. Rebuilt two import blocks the auto-merge silently truncated
(node-arrow-handles.tsx, duct-fitting/move-tool.tsx).

Verified: tsc clean across core/viewer/editor/nodes/mcp, 451 tests pass,
biome clean. Floorplan view-transform re-render storm confirmed pre-existing
(not introduced by this merge).

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

packages/core/src/hooks/scene-registry/item-clip-registry.ts

@@ -0,0 +1,19 @@
+import type * as THREE from 'three'
+
+export type ItemClipEntry = {
+  /** The catalog clip to re-emit (e.g. a fan's "On" spin). */
+  clip: THREE.AnimationClip
+  /** Plays looping in the baked viewer (ambient motion) vs once. */
+  loop: boolean
+}
+
+/**
+ * Catalog-item animation clips the bake needs to re-emit. A catalog GLB ships
+ * its own clips (the live item renderer loads + plays them), but those clips
+ * are not part of the editor scene graph, so the GLB export can't see them on
+ * its own. The item renderer registers the resolved clip per node id while the
+ * scene is live; `glb-export` reads this and retargets the clip onto the baked
+ * item subtree. Door/window motion is synthesized separately and never goes
+ * here. Keyed by node id; cleared with the rest of the scene refs on unload.
+ */
+export const itemClipRegistry = new Map<string, ItemClipEntry>()