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/definition.ts

@@ -54,6 +54,19 @@ export const slabDefinition: NodeDefinition<typeof SlabNode> = {
 
   parametrics: slabParametrics,
 
+  // Stage D: kind-owned placement tool. Multi-click polygon drawing
+  // with axis/45° snap (Shift to defeat).
+  tool: () => import('./tool'),
+
+  // Stage D: drag/edit affordances. Boundary editor + hole editor
+  // delegate to the shared `<PolygonEditor>`; move uses the single-
+  // undo dance for the polygon-translate commit.
+  affordanceTools: {
+    'boundary-edit': () => import('./boundary-editor'),
+    'hole-edit': () => import('./hole-editor'),
+    move: () => import('./move-tool'),
+  },
+
   // Stage B: pure geometry function.
   geometry: buildSlabGeometry,
   // Stage C: floor-plan rendering. Legacy `slabPolygons` short-circuits