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/guide/renderer.tsx

@@ -0,0 +1,72 @@
+'use client'
+
+import { type GuideNode, useRegistry } from '@pascal-app/core'
+import { useAssetUrl, useViewer } from '@pascal-app/viewer'
+import { useLoader } from '@react-three/fiber'
+import { Suspense, useMemo, useRef } from 'react'
+import { DoubleSide, type Group, type Texture, TextureLoader } from 'three'
+import { float, texture } from 'three/tsl'
+import { MeshBasicNodeMaterial } from 'three/webgpu'
+
+export const GuideRenderer = ({ node }: { node: GuideNode }) => {
+  const showGuides = useViewer((s) => s.showGuides)
+  const ref = useRef<Group>(null!)
+  useRegistry(node.id, 'guide', ref)
+
+  const resolvedUrl = useAssetUrl(node.url)
+
+  return (
+    <group
+      position={node.position}
+      ref={ref}
+      rotation={[0, node.rotation[1], 0]}
+      visible={showGuides && node.visible !== false}
+    >
+      {resolvedUrl && (
+        <Suspense>
+          <GuidePlane opacity={node.opacity} scale={node.scale} url={resolvedUrl} />
+        </Suspense>
+      )}
+    </group>
+  )
+}
+
+const GuidePlane = ({ url, scale, opacity }: { url: string; scale: number; opacity: number }) => {
+  const tex = useLoader(TextureLoader, url) as Texture
+
+  const { width, height, material } = useMemo(() => {
+    const img = tex.image as HTMLImageElement | ImageBitmap
+    const w = img.width || 1
+    const h = img.height || 1
+    const aspect = w / h
+
+    // Default: 10 meters wide, height from aspect ratio
+    const planeWidth = 10 * scale
+    const planeHeight = (10 / aspect) * scale
+
+    const normalizedOpacity = opacity / 100
+
+    const mat = new MeshBasicNodeMaterial({
+      transparent: true,
+      colorNode: texture(tex),
+      opacityNode: float(normalizedOpacity),
+      side: DoubleSide,
+      depthWrite: false,
+    })
+
+    return { width: planeWidth, height: planeHeight, material: mat }
+  }, [tex, scale, opacity])
+
+  return (
+    <mesh
+      frustumCulled={false}
+      material={material}
+      raycast={() => {}}
+      rotation={[-Math.PI / 2, 0, 0]}
+    >
+      <planeGeometry args={[width, height]} boundingBox={null} boundingSphere={null} />
+    </mesh>
+  )
+}
+
+export default GuideRenderer