Phase 5 Stage D slab: port placement + move + boundary/hole editors

Replicates the fence Stage D recipe for slab — three drag affordances
+ one placement tool, all routed through the registry:

  affordanceTools:
    'boundary-edit' → thin <PolygonEditor> wrapper (vertex/edge drag)
    'hole-edit'     → same for a single hole polygon
    move            → DragAction with single-undo dance
  tool: () => placement (multi-click polygon with axis/45° snap)

`PolygonEditor` + `PolygonEditorProps` exported from
`@pascal-app/editor` as Stage D transitional surface (Stage F cleanup
moves them into `@pascal-app/nodes`).

ToolManager mount sites for SlabBoundaryEditor / SlabHoleEditor now
route through `getRegistryAffordanceTool` with legacy fallback.

Slab move action does not use the live-drag exception (polygon CSG
rebuild every tick) — matches legacy behavior; optimization is a
separate task once we measure.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/nodes/src/slab/hole-editor.tsx

@@ -0,0 +1,53 @@
+'use client'
+
+import { resolveLevelId, type SlabNode, useScene } from '@pascal-app/core'
+import { PolygonEditor } from '@pascal-app/editor'
+import { useViewer } from '@pascal-app/viewer'
+import { useCallback } from 'react'
+
+/**
+ * Phase 5 Stage D — slab hole editor (registry-driven).
+ *
+ * Edits a specific hole polygon inside a slab. Mounted by ToolManager
+ * via `def.affordanceTools['hole-edit']` when `useEditor.editingHole`
+ * is set on the selected slab.
+ */
+export const SlabHoleEditor: React.FC<{ slabId: SlabNode['id']; holeIndex: number }> = ({
+  slabId,
+  holeIndex,
+}) => {
+  const slabNode = useScene((s) => s.nodes[slabId])
+  const updateNode = useScene((s) => s.updateNode)
+  const setSelection = useViewer((s) => s.setSelection)
+
+  const slab = slabNode?.type === 'slab' ? (slabNode as SlabNode) : null
+  const holes = slab?.holes || []
+  const hole = holes[holeIndex]
+
+  const handlePolygonChange = useCallback(
+    (newPolygon: Array<[number, number]>) => {
+      const updatedHoles = [...holes]
+      updatedHoles[holeIndex] = newPolygon
+      updateNode(slabId, { holes: updatedHoles })
+      setSelection({ selectedIds: [slabId] })
+    },
+    [slabId, holeIndex, holes, updateNode, setSelection],
+  )
+
+  if (!(slab && hole) || hole.length < 3) return null
+
+  return (
+    <PolygonEditor
+      allowEdgeMove
+      allowPolygonMove
+      color="#ef4444"
+      levelId={resolveLevelId(slab, useScene.getState().nodes)}
+      minVertices={3}
+      onPolygonChange={handlePolygonChange}
+      polygon={hole}
+      surfaceHeight={slab.elevation ?? 0.05}
+    />
+  )
+}
+
+export default SlabHoleEditor