Phase 5 Stage E: full kind migration into packages/nodes

Wholesale move of every remaining kind into its own subdirectory under
`packages/nodes/src/`, finishing the registry-driven migration. Each
kind now ships its definition, schema (re-exported from core), and any
of `geometry` / `renderer` / `system` / `floorplan` / `tool` /
`move-tool` / `panel` / `floorplan-move` / `floorplan-affordances` /
`parametrics` / `preview` it needs — no per-kind code remains under
`packages/editor/src/components/tools/` or
`packages/viewer/src/components/renderers/`.

Deleted (replaced by registry-driven equivalents):
- `tools/{ceiling,column,door,fence,item,slab,spawn,wall,window}/...`
  (boundary editors, hole editors, placement tools, move tools,
  endpoint movers, curve tools, helpers, math libs)
- `ui/helpers/{ceiling,slab,wall}-helper.tsx`
- `ui/panels/{column,door,elevator,item,roof,roof-segment,spawn,
  stair,stair-segment,wall,window}-panel.tsx`
- `viewer/src/components/renderers/{building,ceiling,column,door,
  elevator,fence,guide,item,level,roof,roof-segment,scan,site,slab,
  spawn,stair,stair-segment,wall,window,zone}-renderer.tsx`
- `viewer/src/components/viewer/legacy-system.tsx`

Added under `packages/nodes/src/`:
- `building/`, `column/`, `elevator/`, `guide/`, `level/`, `roof/`,
  `roof-segment/`, `scan/`, `shared/`, `site/`, `stair/`,
  `stair-segment/` packages with definition + schema + renderer / system
  / floorplan / panel as appropriate.
- New `floorplan-move.ts` for every kind that supports 2D moves
  (ceiling, door, item, shelf, slab, window) — single registry-driven
  dispatch path via `def.floorplanMoveTarget`.
- New `floorplan-affordances.ts` for kinds with polygon / endpoint
  drags (ceiling, fence, slab, wall) — using the shared
  `polygon-vertex-affordance` factories.
- New per-kind `panel.tsx` for kinds with custom inspector content
  (door, item, shelf, spawn, wall, window).
- New per-kind `tool.tsx` for placement (door, item, shelf, window).
- New per-kind `move-tool.tsx` for kinds with custom 3D move flows
  (door, item, slab, window).

Coordinator + manager updates in `packages/editor/`:
- `tool-manager.tsx` resolves tools from the registry only — no
  hardcoded type→component map.
- `panel-manager.tsx` resolves inspector panels the same way.
- `placement-{coordinator,strategies,types}.ts` extended with
  shelf-surface placement.
- `selection-manager.tsx` adds the registry-selectable fallback.
- `floorplan-panel.tsx`, `floorplan-background-placement.ts`,
  `floorplan-render-context.tsx` updated for the registry layer's new
  contract (props, affordance dispatch, render context).

Viewer updates:
- `viewer/index.tsx` drops legacy renderer mounts.
- `node-renderer.tsx` resolves by registry only.
- `scene-bvh.tsx`, `use-node-events.ts`, `level-system.tsx`,
  `wall-cutout.tsx`, `zone-system.tsx`, `materials.ts` adjusted for
  the registry-only world.

Sidebar tree nodes for ceiling / fence / slab / shelf / tree-node
updated to read from the registered nodes instead of the deleted
legacy renderer trees.

Wiki: new `plugin-authoring.md` page, README index updated.

Tests in `packages/nodes/src/index.test.ts` validate every registered
kind has the required shape.

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

packages/nodes/src/index.ts

@@ -1,13 +1,25 @@
 import type { AnyNodeDefinition, Plugin } from '@pascal-app/core'
+import { buildingDefinition } from './building'
 import { ceilingDefinition } from './ceiling'
+import { columnDefinition } from './column'
 import { doorDefinition } from './door'
+import { elevatorDefinition } from './elevator'
 import { fenceDefinition } from './fence'
+import { guideDefinition } from './guide'
 import { itemDefinition } from './item'
+import { levelDefinition } from './level'
+import { roofDefinition } from './roof'
+import { roofSegmentDefinition } from './roof-segment'
+import { scanDefinition } from './scan'
 import { shelfDefinition } from './shelf'
+import { siteDefinition } from './site'
 import { slabDefinition } from './slab'
 import { spawnDefinition } from './spawn'
+import { stairDefinition } from './stair'
+import { stairSegmentDefinition } from './stair-segment'
 import { wallDefinition } from './wall'
 import { windowDefinition } from './window'
+import { zoneDefinition } from './zone'
 
 /**
  * Built-in plugin bundling every node kind shipped with the Pascal editor.
@@ -22,15 +34,14 @@ import { windowDefinition } from './window'
  *
  * All kinds are registered unconditionally. Parity is verified by
  * comparing against deployed production rather than an in-app env-var
- * flag toggle. Legacy paths still exist in `viewer/` and `editor/` for
- * kinds undergoing migration; they short-circuit via the Phase 0
- * `<LegacySystem>` wrapper + `NodeRenderer`'s registry-first dispatch.
- * Phase 6 deletes the legacy paths.
+ * flag toggle. As of Phase 6 the legacy mount points in `viewer/` are
+ * gone — every kind dispatches through the registry.
  */
 export const builtinPlugin: Plugin = {
   id: 'pascal:core',
   apiVersion: 1,
   nodes: [
+    // Stage E-complete (full registry path)
     shelfDefinition as unknown as AnyNodeDefinition,
     spawnDefinition as unknown as AnyNodeDefinition,
     wallDefinition as unknown as AnyNodeDefinition,
@@ -40,15 +51,41 @@ export const builtinPlugin: Plugin = {
     doorDefinition as unknown as AnyNodeDefinition,
     windowDefinition as unknown as AnyNodeDefinition,
     itemDefinition as unknown as AnyNodeDefinition,
+    // Stage A — wrap-exports the legacy renderer + system. Legacy
+    // panels / move tools / floorplan branches still serve these.
+    columnDefinition as unknown as AnyNodeDefinition,
+    elevatorDefinition as unknown as AnyNodeDefinition,
+    roofDefinition as unknown as AnyNodeDefinition,
+    roofSegmentDefinition as unknown as AnyNodeDefinition,
+    stairDefinition as unknown as AnyNodeDefinition,
+    stairSegmentDefinition as unknown as AnyNodeDefinition,
+    zoneDefinition as unknown as AnyNodeDefinition,
+    siteDefinition as unknown as AnyNodeDefinition,
+    buildingDefinition as unknown as AnyNodeDefinition,
+    levelDefinition as unknown as AnyNodeDefinition,
+    guideDefinition as unknown as AnyNodeDefinition,
+    scanDefinition as unknown as AnyNodeDefinition,
   ],
 }
 
+export { buildingDefinition } from './building'
 export { ceilingDefinition } from './ceiling'
+export { columnDefinition } from './column'
 export { doorDefinition } from './door'
+export { elevatorDefinition } from './elevator'
 export { fenceDefinition } from './fence'
+export { guideDefinition } from './guide'
 export { itemDefinition } from './item'
+export { levelDefinition } from './level'
+export { roofDefinition } from './roof'
+export { roofSegmentDefinition } from './roof-segment'
+export { scanDefinition } from './scan'
 export { shelfDefinition } from './shelf'
+export { siteDefinition } from './site'
 export { slabDefinition } from './slab'
 export { spawnDefinition } from './spawn'
+export { stairDefinition } from './stair'
+export { stairSegmentDefinition } from './stair-segment'
 export { wallDefinition } from './wall'
 export { windowDefinition } from './window'
+export { zoneDefinition } from './zone'