MVP M5.9: SQLite persistence via Prisma + optimistic-local sync

State now survives a page refresh. Every applied op writes a fresh model
snapshot + a changelog row inside one transaction; the editor route
server-component loads the latest snapshot and seeds it as the initial
ModelStore state. Optimistic-local apply on the client + background POST
to /api/projects/[id]/apply gives the UI an instant feel without giving
up the server-as-truth contract.

apps/web/prisma
- schema.prisma: Project / ModelSnapshot / ChangelogEntry. SQLite for dev
  (file:./dev.db). The same schema swaps to Postgres by changing the
  provider line + DATABASE_URL.

apps/web/lib/db
- client.ts: PrismaClient singleton with hot-reload guard.
- repo.ts: loadProject() auto-seeds Aristotle from fromFixture();
  applyOpsToProject() runs the pure applyOps() server-side inside a
  $transaction, writes the snapshot + changelog atomically, returns
  { applied, model, version, idMapping, errors }. Optimistic-concurrency
  via expectedVersion → returns the server model on mismatch so the
  client can resync without losing its tab.

apps/web/app/api/projects/[projectId]
- route.ts (GET): returns latest { model, version }
- apply/route.ts (POST): body is { ops, expectedVersion?, reason? }

apps/web/lib/sync/ModelStore.tsx
- Now takes initialModel + initialVersion + projectId. apply() updates
  local state immediately, then POSTs in the background. On response the
  authoritative server model + version replace the optimistic state
  (handles tempId resolution from the server). Network errors keep the
  optimistic state; the next successful apply reconciles.

apps/web/app/editor/[projectId]/page.tsx
- Server component now: awaits loadProject(projectId), passes initialModel
  + initialVersion + projectId to EditorShell. EditorShell falls back to
  the fixture path when those props are absent (legacy callers / tests).

package.json
- pnpm.onlyBuiltDependencies allowlists prisma + @prisma/client + @prisma/engines
- db:push / db:generate / db:reset scripts

.gitignore
- apps/web/prisma/dev.db + dev.db-journal excluded.

Pinned to prisma@6 (prisma@7 dropped url from schema in favor of the
new adapter pattern; not worth the churn for MVP).

apps/web/package.json

@@ -6,9 +6,20 @@
     "dev": "next dev",
     "build": "next build",
     "start": "next start",
-    "lint": "eslint"
+    "lint": "eslint",
+    "db:push": "prisma db push --skip-generate",
+    "db:generate": "prisma generate",
+    "db:reset": "rm -f prisma/dev.db && pnpm db:push && pnpm db:generate"
+  },
+  "pnpm": {
+    "onlyBuiltDependencies": [
+      "@prisma/client",
+      "@prisma/engines",
+      "prisma"
+    ]
   },
   "dependencies": {
+    "@prisma/client": "^6.19.3",
     "@tiptap/core": "^3.22.5",
     "@tiptap/extension-mention": "^3.22.5",
     "@tiptap/pm": "^3.22.5",
@@ -17,6 +28,7 @@
     "@tiptap/suggestion": "^3.22.5",
     "@xyflow/react": "^12.10.2",
     "next": "16.2.4",
+    "prisma": "^6.19.3",
     "react": "19.2.4",
     "react-dom": "19.2.4"
   },