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/app/api/projects/[projectId]/apply/route.ts

@@ -0,0 +1,25 @@
+// POST /api/projects/[projectId]/apply — body is { ops: ModelOp[], expectedVersion?: number, reason?: string }.
+// Returns { applied, model, version, idMapping, errors } from the server-side applyOps.
+
+import { NextResponse } from "next/server";
+import { applyOpsToProject } from "../../../../../lib/db/repo";
+import type { ModelOp } from "../../../../../lib/sync/ops";
+
+export async function POST(req: Request, { params }: { params: Promise<{ projectId: string }> }) {
+  const { projectId } = await params;
+  let body: { ops?: ModelOp[]; expectedVersion?: number; reason?: string };
+  try {
+    body = await req.json();
+  } catch {
+    return NextResponse.json({ error: "invalid json body" }, { status: 400 });
+  }
+  if (!body.ops || !Array.isArray(body.ops) || body.ops.length === 0) {
+    return NextResponse.json({ error: "body.ops must be a non-empty array" }, { status: 400 });
+  }
+  try {
+    const result = await applyOpsToProject(projectId, body.ops, body.expectedVersion, body.reason);
+    return NextResponse.json(result);
+  } catch (err) {
+    return NextResponse.json({ error: (err as Error).message }, { status: 500 });
+  }
+}

apps/web/app/api/projects/[projectId]/route.ts

@@ -0,0 +1,15 @@
+// GET /api/projects/[projectId] — returns the latest SysMLModel + version.
+// Auto-seeds Aristotle if the project doesn't exist yet.
+
+import { NextResponse } from "next/server";
+import { loadProject } from "../../../../lib/db/repo";
+
+export async function GET(_req: Request, { params }: { params: Promise<{ projectId: string }> }) {
+  const { projectId } = await params;
+  try {
+    const result = await loadProject(projectId);
+    return NextResponse.json(result);
+  } catch (err) {
+    return NextResponse.json({ error: (err as Error).message }, { status: 500 });
+  }
+}