chore(studio): move the TanStack Start deploy onto Nitro (#50030)

Moves the Studio TanStack Start build off the hand-rolled Vercel setup
(an `api/server.js` function shim, rewrites in `vercel.ts`, a custom
`?dpl=` skew-protection Vite plugin, and `scripts/serve.js` for
self-hosted) and onto Nitro, which TanStack Start documents as its
deployment path. Documents are served from the static SPA shell on the
CDN; only `/api/*` and `/_serverFn/*` invoke the function.

**Removed:**
- `api/server.js`, `scripts/serve.js`, `scripts/smoke-server.mjs`
- The `skewProtectionDpl` Vite plugin, `renderBuiltUrl`, and the
`vite:preloadError` reload backstop in `router.tsx` (TanStack Router
already reloads once on a failed lazy import)
- Rewrites, `functions`, `outputDirectory`, and `cleanUrls` from
`vercel.ts` (redirects and headers stay)
- `magic-string` and `@jridgewell/remapping` devDependencies, the
`preview` script

**Added:**
- `nitro` plugin in `vite.config.ts`. Preset is auto-detected:
`.vercel/output` on Vercel, a self-contained node server in `.output`
everywhere else. `vercel.immutableStaticFiles` puts hashed chunks under
`/_vercel/immutable/` so tabs opened before a redeploy keep loading
their chunks; `functions.maxDuration: 300` carries over the old function
timeout
- `scripts/vercel-spa-routes.ts`: Nitro module that rewrites the
generated Build Output routes (documents -> `_shell.html`, allow-list ->
`__server`, missing chunk -> 404, base-path prefixes), with a unit test
- `server.ts`: TanStack Start server entry that initializes Sentry
before the route tree loads and wraps the handler with
`wrapFetchWithSentry`

**Changed:**
- `start:tanstack` runs `.output/server/index.mjs` directly with Node's
`--env-file-if-exists` for the `.env` cascade. Node doesn't expand
`$VAR` references, so `scripts/generateLocalEnv.js` now writes literal
values into `.env.test`
- Dockerfile's TanStack stage copies `.output` instead of running `pnpm
deploy`; the `server.js` shim loads `.env` and imports the Nitro server
- `NEXT_PUBLIC_BASE_PATH` (the platform's `/dashboard`) only sets the
router basepath; Vite's `base` stays at the root so chunks can use the
immutable store. The routes module emits prefixed rules for
`/dashboard/api/*` and `/dashboard/_serverFn/*` and rewrites `public/`
files requested under the prefix back to the root
- Self-hosted security headers come from a Nitro `routeRules` entry; on
Vercel they stay in `vercel.ts`
- `tslib` is inlined for the build only: Nitro's dev runner has no
interop for its CJS wrapper
- Monaco's worker chunks follow the client assets dir so they land in
the immutable store too

Verified on the `studio-staging` preview (`STUDIO_FRAMEWORK=tanstack` is
scoped to this branch there): documents come back as the static shell,
`/dashboard/api/*` hits the function, `public/` files resolve under the
prefix, a missing immutable chunk 404s. Across two deployments of this
branch, the older deployment's chunks still load from the immutable
store and requests carrying its `__vdpl` cookie are answered by that
deployment. Self-hosted path covered by the TanStack E2E job and the
Docker build job.

## To test

- On the `studio-staging` preview: `/dashboard/project/<ref>` should
show `content-disposition: inline; filename="_shell.html"` and a
single-region `x-vercel-id`; `/dashboard/api/get-utc-time` a two-region
id
- Sign in and click through a few pages, including one that opens Monaco
(SQL editor) so the worker chunks load
- After the next deploy, a tab left open on the previous one should
still navigate (lazy chunks) and call the API without errors
- Self-hosted: `STUDIO_FRAMEWORK=tanstack pnpm --filter studio build &&
pnpm --filter studio start`, then check `/api/platform/profile` and that
responses carry the security headers


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Production TanStack deployments now run on Nitro’s self-contained
server output.
* Vercel routing serves static pages first while directing API and
server-function requests appropriately.
* Server-function requests can include deployment identification for
consistent handling.
* Local environment generation now writes resolved configuration values.

* **Bug Fixes**
  * Improved handling of missing static assets and SPA fallback routing.
* Server-side error monitoring now captures request errors in the new
runtime.

* **Refactor**
* Replaced the legacy production server and smoke-test workflow with
Nitro-based startup.
  * Removed automatic reload handling for stale client assets.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Alaister Young <10985857+alaister@users.noreply.github.com>

apps/studio/package.json

@@ -9,14 +9,12 @@
     "dev": "node scripts/dispatch.js dev",
     "build": "node scripts/dispatch.js build",
     "start": "node scripts/dispatch.js start",
-    "preview": "vite preview --mode ${MODE:-production} --port 8082",
     "dev:next": "next dev -p ${STUDIO_PORT:-8082}",
     "build:next": "next build && if [ \"$SKIP_ASSET_UPLOAD\" != \"1\" ]; then ./../../scripts/upload-static-assets.sh; fi",
     "start:next": "next start -p 8082",
     "dev:tanstack": "NODE_OPTIONS=--max-old-space-size=8192 vite dev --port ${STUDIO_PORT:-8082}",
-    "build:tanstack": "vite build --mode ${MODE:-production} && pnpm smoke:tanstack",
-    "smoke:tanstack": "node scripts/smoke-server.mjs",
-    "start:tanstack": "node scripts/serve.js",
+    "build:tanstack": "vite build --mode ${MODE:-production}",
+    "start:tanstack": "node --env-file-if-exists=.env --env-file-if-exists=.env.local --env-file-if-exists=.env.${MODE:-production} --env-file-if-exists=.env.${MODE:-production}.local .output/server/index.mjs",
     "lint": "eslint .",
     "lint:ratchet": "tsx scripts/ratchet-eslint-rules.ts --rules-file scripts/ratchet-rules.json",
     "clean": "rimraf .next .turbo tsconfig.tsbuildinfo",
@@ -168,7 +166,6 @@
     "@faker-js/faker": "^9.9.0",
     "@graphql-codegen/cli": "5.0.5",
     "@graphql-typed-document-node/core": "^3.2.0",
-    "@jridgewell/remapping": "^2.3.5",
     "@tailwindcss/postcss": "^4.2.4",
     "@tailwindcss/vite": "4.2.4",
     "@tanstack/devtools-vite": "^0.6.0",
@@ -205,9 +202,9 @@
     "graphql-ws": "5.14.1",
     "import-in-the-middle": "^2.0.0",
     "jsdom-testing-mocks": "^1.13.1",
-    "magic-string": "^0.30.21",
     "msw": "^2.3.0",
     "next-router-mock": "^0.9.13",
+    "nitro": "3.0.260903-beta",
     "node-mocks-http": "^1.17.2",
     "postcss": "catalog:",
     "raw-loader": "^4.0.2",