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/prisma/schema.prisma

@@ -0,0 +1,54 @@
+// SQLite-backed dev persistence (M5.9). The model is stored as a JSON snapshot
+// per project + a changelog of applied ops. This is the smallest shape that
+// gives us "refresh persists state" without committing to the full
+// event-sourced architecture in docs/sync.md (that lands later).
+//
+// Switch `provider` to "postgresql" + set DATABASE_URL=postgres://… to move
+// to a real DB later — schema is portable.
+
+generator client {
+  provider = "prisma-client-js"
+}
+
+datasource db {
+  provider = "sqlite"
+  url      = "file:./dev.db"
+}
+
+model Project {
+  id        String   @id
+  name      String
+  scope     String
+  tagline   String
+  createdAt DateTime @default(now())
+  updatedAt DateTime @updatedAt
+
+  snapshots ModelSnapshot[]
+  changes   ChangelogEntry[]
+}
+
+model ModelSnapshot {
+  id        String   @id @default(cuid())
+  projectId String
+  version   Int
+  json      String   // serialized SysMLModel
+  createdAt DateTime @default(now())
+
+  project   Project @relation(fields: [projectId], references: [id], onDelete: Cascade)
+
+  @@unique([projectId, version])
+  @@index([projectId, version])
+}
+
+model ChangelogEntry {
+  id        String   @id @default(cuid())
+  projectId String
+  version   Int      // resulting model version after these ops landed
+  ops       String   // JSON-encoded ModelOp[]
+  reason    String?  // optional human/Socrates-supplied rationale
+  createdAt DateTime @default(now())
+
+  project   Project @relation(fields: [projectId], references: [id], onDelete: Cascade)
+
+  @@index([projectId, version])
+}