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/tools/scene-lifecycle/index.ts

@@ -0,0 +1,32 @@
+import type { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js'
+import type { SceneBridge } from '../../bridge/scene-bridge'
+import type { SceneStore } from '../../storage/types'
+import { registerDeleteScene } from './delete-scene'
+import { registerListScenes } from './list-scenes'
+import { registerLoadScene } from './load-scene'
+import { registerRenameScene } from './rename-scene'
+import { registerSaveScene } from './save-scene'
+
+/**
+ * Register the scene-lifecycle MCP tools (`save_scene`, `load_scene`,
+ * `list_scenes`, `delete_scene`, `rename_scene`) against the given server.
+ * All tools operate against the supplied `SceneStore` so tests can inject an
+ * in-memory implementation.
+ */
+export function registerSceneLifecycleTools(
+  server: McpServer,
+  bridge: SceneBridge,
+  store: SceneStore,
+): void {
+  registerSaveScene(server, bridge, store)
+  registerLoadScene(server, bridge, store)
+  registerListScenes(server, store)
+  registerDeleteScene(server, store)
+  registerRenameScene(server, store)
+}
+
+export { deleteSceneInput, deleteSceneOutput, registerDeleteScene } from './delete-scene'
+export { listScenesInput, listScenesOutput, registerListScenes } from './list-scenes'
+export { loadSceneInput, loadSceneOutput, registerLoadScene } from './load-scene'
+export { registerRenameScene, renameSceneInput, renameSceneOutput } from './rename-scene'
+export { registerSaveScene, saveSceneInput, saveSceneOutput } from './save-scene'