CI build fails on every run since March — Node 18 doesn't provide @oxc-parser native bindings #10

Describe the bug

The `Deploy to Vercel` workflow has failed on every run since Mar 8 2026 (last green was `c53167f` on Nov 22 2025). It builds on Node 18, and under Node 18, pnpm silently skips the platform-specific `@oxc-parser` native binding when resolving `oxc-parser`'s optional dependencies. Optional deps fail quietly, so `pnpm install --frozen-lockfile` still exits 0 — the tree is just two packages short. Nothing complains until unocss loads `uno.config.ts` through jiti, at which point the build dies with:

```
Cannot find module '@oxc-parser/binding-linux-x64-gnu'
```

That happens inside Astro's content-collection sync, so the visible symptom is `astro check` aborting about two seconds in — reads like a config/content error, not a dependency error.

Steps to reproduce

1. Install on Node 18.20.8 with the repo's lockfile — install exits 0, but `node_modules/@oxc-parser` is absent.
2. Run `pnpm run build` (or `astro check`) — fails in ~3s.
3. Repeat on Node 22.22.2 with the same lockfile — `node_modules/@oxc-parser` has both bindings, `pnpm run build` succeeds (215 pages).

Expected behavior

CI builds on the Node version this repo actually requires (22, per `.tool-versions`) and succeeds.

Additional context

Node 18 also reached end-of-life in April 2025. Fixed in #9.