Fourth and final Stage D fence affordance — the placement tool itself.
Unlike the drag affordances (curve / move / endpoint), placement is a
two-click flow with state across grid events, not a single drag-down →
drag-up lifecycle. `DragAction` doesn't fit; the component owns its
own emitter subscriptions directly. The kind exposes it via
`def.tool: () => import('./tool')` and ToolManager's existing
`getRegistryTool()` lookup mounts it (legacy `tools.structure.fence =
FenceTool` falls through when the registry entry is missing).
Adds transitional exports from `@pascal-app/editor` for the helpers
the kind-owned tool needs at module scope: `createFenceOnCurrentLevel`,
`markToolCancelConsumed`, `EDITOR_LAYER`. Stage F cleanup moves these
into `@pascal-app/nodes` once every consumer is registry-driven.
Fence Stage D is now complete. Per-kind progress: A ✅ B ✅ C ✅ D ✅
(four affordances ported — curve, move-endpoint, move, placement).
E (drop legacy panel) and F (cleanup) pending across all kinds.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
