feat(editor): mode-driven shelf/column/spawn placement + cross-kind floor collision

Migrate the remaining floor-placed kinds onto the unified snapping/modifier
model and generalize floor collision so any solid floor kind blocks any other.

- shelf/column/spawn declare `snapProfile: 'item'` → contextual snapping chip,
  Shift=cycle, Ctrl=grid step during placement; their tools read the active
  mode (grid/lines/off) instead of legacy Shift/Alt bypass; spawn fresh
  placement now respects alignment ("lines") like its move.
- Resize/radial handles claim the handle-drag scope (new RESIZE_HANDLE_DRAG_LABEL)
  so the HUD shows no select-mode shortcuts mid-resize.
- Column move migrated to the generic MoveRegistryNodeTool (declare `movable`,
  drop the bespoke move-tool) — gains mode-driven snapping, alignment, R/T,
  slab lift, grid SFX, and the collision box for free. 2D move still routes
  through `floorplanMoveTarget`.
- Cross-kind floor collision: new declarative `FloorPlacedConfig.collides`
  (item/shelf/column opt in; spawn/MEP/stair stay off). `canPlaceOnFloor` now
  treats every colliding floor kind as an obstacle (was item-only), reading the
  declarative footprint; the generic move tool's red/green placement box gates
  on `collides`. Column footprint uses the visible `columnFootprintHalf` extent
  so the box/slab-lift/collision track the real (round/square) column size.

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

packages/editor/src/components/editor/node-arrow-handles.tsx

@@ -43,7 +43,7 @@ import { mergeGeometries } from 'three/examples/jsm/utils/BufferGeometryUtils.js
 
 import { MeshBasicNodeMaterial } from 'three/webgpu'
 import { EDITOR_LAYER } from '../../lib/constants'
-import { ROTATE_HANDLE_DRAG_LABEL } from '../../lib/contextual-help'
+import { RESIZE_HANDLE_DRAG_LABEL, ROTATE_HANDLE_DRAG_LABEL } from '../../lib/contextual-help'
 import { createEditorApi } from '../../lib/editor-api'
 import { sfxEmitter } from '../../lib/sfx-bus'
 import useDirectManipulationFeedback from '../../store/use-direct-manipulation-feedback'
@@ -681,16 +681,18 @@ function LinearArrow({
       return {
         overrideId,
         onBegin: () => {
-          if (measureLabel) {
-            useInteractionScope
-              .getState()
-              .begin({ kind: 'handle-drag', nodeId, handle: measureLabel })
-          }
+          // Always claim the handle-drag scope so the HUD knows a resize is the
+          // active interaction (keeps the idle select hints off-screen). The
+          // dimension-pill handles carry their `measureLabel`; plain resize
+          // arrows use the generic label.
+          useInteractionScope.getState().begin({
+            kind: 'handle-drag',
+            nodeId,
+            handle: measureLabel ?? RESIZE_HANDLE_DRAG_LABEL,
+          })
         },
         onEnd: () => {
-          if (measureLabel) {
-            useInteractionScope.getState().endIf((sc) => sc.kind === 'handle-drag')
-          }
+          useInteractionScope.getState().endIf((sc) => sc.kind === 'handle-drag')
           if (onDrag) useOpeningGuides.getState().clear()
         },
         move: ({ event: moveEvent, getPointerRay: getMovePointerRay }) => {

packages/editor/src/components/tools/registry/move-registry-node-tool.tsx

@@ -220,18 +220,19 @@ export function MoveRegistryNodeTool({ node }: { node: AnyNode }) {
   // commit / cancel / unmount so a follow-on drag starts clean.
   const overriddenIdsRef = useRef<AnyNodeId[]>([])
 
-  // Shelf placement shows the same green/red footprint box GLB items use
-  // (instead of the vertical-arrow cursor) and refuses an invalid drop unless
-  // Shift forces it. The footprint comes from the kind's `floorPlaced`
-  // capability so this stays generic if we ever opt other kinds in.
-  const isShelf = node.type === 'shelf'
+  // Colliding floor kinds (item / shelf / column) show the same green/red
+  // footprint box GLB items use (instead of the vertical-arrow cursor) and
+  // refuse an invalid drop unless Alt forces it. The gate + footprint both come
+  // from the kind's declarative `floorPlaced` capability, so opting a new kind
+  // in is just `collides: true` — no change here.
+  const collides = nodeRegistry.get(node.type)?.capabilities?.floorPlaced?.collides === true
   const boxDimensions = useMemo(
     () =>
-      isShelf
+      collides
         ? (nodeRegistry.get(node.type)?.capabilities?.floorPlaced?.footprint?.(node)?.dimensions ??
           null)
         : null,
-    [isShelf, node],
+    [collides, node],
   )
   const [valid, setValid] = useState(true)
   const [cursorRotationY, setCursorRotationY] = useState(originalRotationY)

packages/editor/src/lib/contextual-help.ts

@@ -10,6 +10,12 @@ export type ContextualShortcutHint = {
 // which route their own measurement label here.
 export const ROTATE_HANDLE_DRAG_LABEL = 'rotate-handle'
 
+// `activeHandleDrag.label` a plain resize / radial-resize arrow sets while
+// dragging (when it carries no dimension `measureLabel`). It exists only so the
+// interaction scope is non-idle during a resize, which keeps the idle
+// select-mode hints off-screen — a resize is its own action, not a selection.
+export const RESIZE_HANDLE_DRAG_LABEL = 'resize-handle'
+
 // Hints shown while a rotate gizmo is mid-drag: Shift bypasses the angle step
 // (free rotation), the same toggle wall drafting exposes. `active` lights the
 // pill while Shift is held.