feat: add iOS simulator worktree preview

Adds the worktree service, setup cache seeding, and Metro preview mount for /.sim. Also includes the related startup and mobile sidebar fixes needed by the updated worktree app flow.

packages/app/package.json

@@ -125,6 +125,7 @@
     "jsdom": "^20.0.3",
     "material-icon-theme": "^5.32.0",
     "playwright": "^1.56.1",
+    "serve-sim": "^0.1.40",
     "typescript": "~5.9.2",
     "vitest": "^4.1.6",
     "wrangler": "^4.75.0",