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.test.ts

@@ -1,5 +1,5 @@
 import { beforeEach, describe, expect, test } from 'bun:test'
-import { loadPlugin, nodeRegistry } from '@pascal-app/core'
+import { AnyNode, loadPlugin, nodeRegistry } from '@pascal-app/core'
 import { builtinPlugin } from './index'
 
 describe('builtinPlugin', () => {
@@ -15,10 +15,32 @@ describe('builtinPlugin', () => {
 
   test('loads the registered kinds without error', async () => {
     await loadPlugin(builtinPlugin)
-    // Phase 2 registers shelf unconditionally; spawn is flag-gated. So the
-    // registry should always contain shelf, and may contain spawn depending
-    // on the NEXT_PUBLIC_USE_REGISTRY_FOR_SPAWN env value at module load.
     expect(nodeRegistry.has('shelf')).toBe(true)
     expect(nodeRegistry.size).toBeGreaterThanOrEqual(1)
   })
+
+  test('every AnyNode discriminator is registered in builtinPlugin', async () => {
+    // Phase 6 coverage check. The `AnyNode` discriminated union and the
+    // `builtinPlugin.nodes` array are both hand-maintained today (full
+    // codegen would have to run at module-load time, which loses the
+    // static node typing TypeScript relies on). This test makes drift a
+    // CI failure: every node `type` literal in the union must have a
+    // matching `def.kind` in the plugin, and vice versa.
+    //
+    // When a kind is added: append it to both `core/src/schema/types.ts`
+    // (the union) and `nodes/src/index.ts` (the plugin), and this test
+    // will keep them honest.
+    await loadPlugin(builtinPlugin)
+    const unionKinds = new Set(
+      AnyNode.options.map((option) => {
+        const typeShape = (option as unknown as { shape: { type: { value: string } } }).shape.type
+        return typeShape.value
+      }),
+    )
+    const registryKinds = new Set(Array.from(nodeRegistry.entries(), ([kind]) => kind))
+    const missingFromRegistry = [...unionKinds].filter((k) => !registryKinds.has(k))
+    const missingFromUnion = [...registryKinds].filter((k) => !unionKinds.has(k))
+    expect(missingFromRegistry).toEqual([])
+    expect(missingFromUnion).toEqual([])
+  })
 })