feat(mcp,editor): Option A+B storage + 10 agent deliverables (Phase 7)

Ships the combined filesystem/Supabase storage adapter + MCP scene
lifecycle tools + Next.js API routes + editor /scene/[id] route, so
an MCP save is directly openable at /scene/<id> without any
injection hack. End-to-end verified: 10/10 e2e steps pass.

Storage (A1/A2/A3):
- SceneStore interface + error classes + slug helpers
- FilesystemSceneStore at $PASCAL_DATA_DIR (defaults XDG/~/.pascal)
  with atomic writes, .index sidecar, optimistic locking
- SupabaseSceneStore with scenes + scene_revisions tables, RLS
  migration SQL, mock-backed unit tests
- createSceneStore(env) auto-selects based on SUPABASE_URL +
  SUPABASE_SERVICE_ROLE_KEY

MCP tools (A4, A8, A9, A10):
- save_scene / load_scene / list_scenes / delete_scene / rename_scene
- list_templates / create_from_template (3 seed templates:
  empty-studio, two-bedroom, garden-house)
- generate_variants (7 mutation kinds, seeded RNG, save=true|false)
- photo_to_scene (vision sampling → scene graph → save)

Editor (A5, A6):
- /api/scenes + /api/scenes/[id] with RFC 7232 If-Match locking
- /scene/[id] and /scenes route pages with save button, SceneLoader
- Removed the window.__pascalScene dev injection hack

Security + UX edges (A7, A8):
- AssetUrl Zod validator: asset:// blob: data:image/ /path https:
  (http://localhost for dev) + PASCAL_ALLOWED_ASSET_ORIGINS env
  allowlist. Hardens scan.url, guide.url, item.asset.src,
  material.texture.url, MaterialMaps.*Map
- Auto-frame camera on empty→non-empty scene transition
  (camera-controls:fit-scene emitter event)

Shared utilities:
- rehydrateSiteChildren() extracted to packages/mcp/src/lib/ and
  used by both create-from-template and generate-variants to work
  around the SiteNode.children-as-objects vs. ids inconsistency
  (CROSS_CUTTING §2)
- Storage + MCP subpath exports added to packages/mcp/package.json
  (CROSS_CUTTING §4)

Tests: 293 pass / 0 fail across 40 files (was 142 pre-Phase-7).
Biome: clean.

Phase-7 e2e script at packages/mcp/test-reports/phase7-e2e.ts:
MCP HTTP + editor Next.js both point at $PASCAL_DATA_DIR =
/tmp/pascal-e2e, save_scene from MCP, GET /api/scenes/<id> from
editor server, /scenes list page renders all saved scenes, scene
page renders SceneLoader, delete_scene works.

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

packages/mcp/src/server.ts

@@ -2,11 +2,22 @@ import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js'
 import type { SceneBridge } from './bridge/scene-bridge'
 import { registerPrompts } from './prompts'
 import { registerResources } from './resources'
+import { createSceneStore } from './storage'
+import type {
+  SceneListOptions,
+  SceneMeta,
+  SceneMutateOptions,
+  SceneSaveOptions,
+  SceneStore,
+  SceneWithGraph,
+} from './storage/types'
 import { registerTools } from './tools'
 import { registerVisionTools } from './tools/vision'
 
 export type CreatePascalMcpServerOptions = {
   bridge: SceneBridge
+  /** Injected `SceneStore`. When omitted, `createSceneStore()` is used lazily. */
+  store?: SceneStore
   name?: string
   version?: string
 }
@@ -16,9 +27,48 @@ export function createPascalMcpServer(opts: CreatePascalMcpServerOptions): McpSe
     name: opts.name ?? 'pascal-mcp',
     version: opts.version ?? '0.1.0',
   })
-  registerTools(server, opts.bridge)
+  const store = opts.store ?? createLazySceneStore()
+  registerTools(server, opts.bridge, store)
   registerVisionTools(server, opts.bridge)
   registerResources(server, opts.bridge)
   registerPrompts(server, opts.bridge)
   return server
 }
+
+/**
+ * Wrap `createSceneStore()` (which is async) behind a synchronous `SceneStore`
+ * facade so that `createPascalMcpServer` can remain synchronous. Each method
+ * resolves the underlying store on first use and memoizes it afterwards.
+ */
+function createLazySceneStore(): SceneStore {
+  let cached: Promise<SceneStore> | null = null
+  const resolve = (): Promise<SceneStore> => {
+    if (!cached) cached = createSceneStore()
+    return cached
+  }
+  return {
+    get backend(): 'filesystem' | 'supabase' {
+      return 'filesystem'
+    },
+    async save(options: SceneSaveOptions): Promise<SceneMeta> {
+      const real = await resolve()
+      return real.save(options)
+    },
+    async load(id: string): Promise<SceneWithGraph | null> {
+      const real = await resolve()
+      return real.load(id)
+    },
+    async list(options?: SceneListOptions): Promise<SceneMeta[]> {
+      const real = await resolve()
+      return real.list(options)
+    },
+    async delete(id: string, options?: SceneMutateOptions): Promise<boolean> {
+      const real = await resolve()
+      return real.delete(id, options)
+    },
+    async rename(id: string, newName: string, options?: SceneMutateOptions): Promise<SceneMeta> {
+      const real = await resolve()
+      return real.rename(id, newName, options)
+    },
+  }
+}