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/roof-segment/renderer.tsx

@@ -0,0 +1,65 @@
+'use client'
+
+import {
+  type AnyNodeId,
+  type RoofNode,
+  type RoofSegmentNode,
+  useRegistry,
+  useScene,
+} from '@pascal-app/core'
+import { getRoofMaterialArray, useNodeEvents, useViewer } from '@pascal-app/viewer'
+import { useEffect, useMemo, useRef } from 'react'
+import * as THREE from 'three'
+import { roofDebugMaterials, roofMaterials } from '../roof/roof-materials'
+
+export const RoofSegmentRenderer = ({ node }: { node: RoofSegmentNode }) => {
+  const ref = useRef<THREE.Mesh>(null!)
+  const nodes = useScene((state) => state.nodes)
+
+  useRegistry(node.id, 'roof-segment', ref)
+
+  const handlers = useNodeEvents(node, 'roof-segment')
+  const debugColors = useViewer((s) => s.debugColors)
+  const parentNode = node.parentId
+    ? (nodes[node.parentId as AnyNodeId] as RoofNode | undefined)
+    : undefined
+  const placeholderGeometry = useMemo(() => {
+    const geometry = new THREE.BufferGeometry()
+    geometry.setAttribute('position', new THREE.Float32BufferAttribute([], 3))
+    geometry.addGroup(0, 0, 0)
+    geometry.addGroup(0, 0, 1)
+    geometry.addGroup(0, 0, 2)
+    geometry.addGroup(0, 0, 3)
+    return geometry
+  }, [])
+
+  const customMaterial = useMemo(() => {
+    if (node.material !== undefined || typeof node.materialPreset === 'string') {
+      return null
+    }
+
+    return parentNode ? getRoofMaterialArray(parentNode) : null
+  }, [node, parentNode])
+
+  const material = debugColors ? roofDebugMaterials : customMaterial || roofMaterials
+
+  useEffect(() => {
+    return () => {
+      placeholderGeometry.dispose()
+    }
+  }, [placeholderGeometry])
+
+  return (
+    <mesh
+      geometry={placeholderGeometry}
+      material={material}
+      position={node.position}
+      ref={ref}
+      rotation-y={node.rotation}
+      visible={node.visible}
+      {...handlers}
+    />
+  )
+}
+
+export default RoofSegmentRenderer