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>
