fix(docs): bound docs build memory to stop Vercel OOM (exit 137) (#3221)

The @objectstack/docs build was killed on Vercel with exit 137 (SIGKILL /
container OOM). The site statically prerenders 400+ MDX pages, and two things
let the build's resident set exceed the 8 GB build container:

1. Next spawns one static-generation worker per CPU. On Vercel's high-core
   build container that fan-out multiplied peak RSS. Cap it with
   `experimental.cpus: 2`.

2. Without an explicit heap ceiling, V8 sizes its max heap from the memory it
   detects and defers GC — in a container that reports host memory rather than
   the cgroup limit, RSS grows past the container limit before GC runs, and the
   kernel SIGKILLs the process (137). Pin the heap with
   `NODE_OPTIONS=--max-old-space-size=4096` so GC keeps RSS bounded.

Verified locally: the full docs build completes cleanly with peak RSS ~4.9 GB
(down from an unbounded ~5.3 GB+), well under the 8 GB container.


Claude-Session: https://claude.ai/code/session_01KjroXa16g7LyNAP3sThibY

Co-authored-by: Claude <noreply@anthropic.com>

Author: os-zhuang

apps/docs/next.config.mjs

@@ -7,6 +7,13 @@ const withMDX = createMDX();
 const config = {
   reactStrictMode: true,
   output: 'standalone',
+  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
+    // multiplied the resident set until the build was OOM-killed (exit 137).
+    // Cap the worker count so peak memory stays well under the container limit.
+    cpus: 2,
+  },
   typescript: {
     ignoreBuildErrors: false,
   },

apps/docs/package.json

@@ -6,7 +6,7 @@
   "license": "Apache-2.0",
   "scripts": {
     "dev": "next dev",
-    "build": "pnpm --filter @objectstack/spec gen:schema && pnpm --filter @objectstack/spec gen:docs && next build",
+    "build": "pnpm --filter @objectstack/spec gen:schema && pnpm --filter @objectstack/spec gen:docs && NODE_OPTIONS='--max-old-space-size=4096' next build",
     "site:start": "next start",
     "site:lint": "next lint",
     "types:check": "fumadocs-mdx && next typegen && tsc --noEmit",