fix(docs): drop output: 'standalone' so the production docs build stops failing

.changeset/docs-drop-standalone-output.md

@@ -0,0 +1,17 @@
+---
+'@objectstack/docs': patch
+---
+
+docs site: drop `output: 'standalone'` so the production build stops failing
+
+The production build of the docs site died at the end of `next build` with
+`ENOENT: no such file or directory, open '.../apps/docs/.next/next-server.js.nft.json'`,
+so nothing merged to `main` reached the site.
+
+That file is opened by the standalone packer (`writeStandaloneDirectory` ->
+`copyTracedFiles`), which Next calls **only** when `output === 'standalone'`.
+Nothing in this repo consumes `.next/standalone` — no Dockerfile, workflow,
+script or config references it, and `docker/Dockerfile` does not build
+`apps/docs` at all — and Vercel does its own serverless packaging. The setting
+served no consumer and was the sole reason that read happened, so removing it
+removes the only code path that can raise this error.

apps/docs/next.config.mjs

@@ -6,7 +6,19 @@ const withMDX = createMDX();
 /** @type {import('next').NextConfig} */
 const config = {
   reactStrictMode: true,
-  output: 'standalone',
+  // No `output: 'standalone'` here on purpose. The standalone packer
+  // (`writeStandaloneDirectory` -> `copyTracedFiles`) opens
+  // `.next/next-server.js.nft.json`, and that open is the ONLY thing in a
+  // production build that reads it. Vercel builds this app with Turbopack via
+  // `vercel.json`'s `pnpm turbo run build --filter=@objectstack/docs`, and the
+  // production build died there with ENOENT on that file while the same cold
+  // build passes locally -- so the trace set is absent under Vercel's builder
+  // specifically. Nothing in this repo consumes `.next/standalone`: no
+  // Dockerfile, workflow, script or config references it, and `docker/Dockerfile`
+  // does not build apps/docs at all. Vercel does its own serverless packaging,
+  // so the setting bought nothing here and cost the whole deployment. If this
+  // app ever gains a self-hosted Node target that needs the standalone bundle,
+  // reintroduce it together with a builder that emits the trace set.
   experimental: {
     // The docs site prerenders 400+ MDX pages. Next spawns one static-generation
     // worker per CPU, and on Vercel's high-core build container that fan-out