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/components/editor/EditorShell.tsx

@@ -22,6 +22,12 @@ import { ModelStoreProvider, useModelStore } from "../../lib/sync/ModelStore";
 
 interface EditorShellProps {
   data: FixtureData;
+  /** Server-loaded initial model + version (M5.9). When omitted, falls back to
+   *  deriving from `data` (legacy fixture path; useful for tests). */
+  initialModel?: import("../../lib/sysml/model").SysMLModel;
+  initialVersion?: number;
+  /** When set, apply() POSTs to /api/projects/[projectId]/apply. */
+  projectId?: string;
   density?: Density;
   markupStyle?: MarkupStyle;
   diagramStyle?: DiagramVariant;
@@ -38,6 +44,9 @@ export function EditorShell(props: EditorShellProps) {
 
 function EditorShellInner({
   data,
+  initialModel,
+  initialVersion,
+  projectId,
   density = "comfortable",
   markupStyle = "color",
   diagramStyle = "softened",
@@ -51,13 +60,19 @@ function EditorShellInner({
     return raw.split(",").map(s => s.trim()).filter((s): s is BreakName => s in BREAKS);
   }, [searchParams]);
 
-  const initialModel = useMemo(() => {
-    const base = fromFixture(data);
+  // Prefer server-loaded model; fall back to fixture derivation for legacy
+  // callers without DB persistence wiring.
+  const startingModel = useMemo(() => {
+    const base = initialModel ?? fromFixture(data);
     return breaks.length > 0 ? applyBreaks(base, breaks) : base;
-  }, [data, breaks]);
+  }, [initialModel, data, breaks]);
 
   return (
-    <ModelStoreProvider initialModel={initialModel}>
+    <ModelStoreProvider
+      initialModel={startingModel}
+      initialVersion={initialVersion ?? 1}
+      projectId={projectId}
+    >
       <ShellBody
         data={data}
         density={density}
@@ -70,14 +85,16 @@ function EditorShellInner({
   );
 }
 
-function ShellBody({
-  data,
-  density,
-  markupStyle,
-  diagramStyle,
-  presence,
-  breaks,
-}: Required<Omit<EditorShellProps, "data">> & { data: FixtureData; breaks: BreakName[] }) {
+interface ShellBodyProps {
+  data: FixtureData;
+  density: Density;
+  markupStyle: MarkupStyle;
+  diagramStyle: DiagramVariant;
+  presence: SocratesPresence;
+  breaks: BreakName[];
+}
+
+function ShellBody({ data, density, markupStyle, diagramStyle, presence, breaks }: ShellBodyProps) {
   const [focusBlockId, setFocusBlockId] = useState<string | null>(null);
   const { model, issues, issuesByElement } = useModelStore();