Skip fetchAgentSkills for www typecheck GHA (#47907)

### Context

Our TS check GHA occasionally runs into GH rate limits because of
`fetchAgentSkills`

### Changes involved
- Opting to omit `fetchAgentSkills` for typecheck
  - `generateStaticContent` is needed still afaict
- Allow GITHUB_TOKEN to be passed for `generateStaticContent`
  - And pass that env var from `typecheck.yml`



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

## Summary by CodeRabbit

- **Improvements**
  - Enhanced reliability of GitHub-powered content during site builds.
- GitHub API requests now use secure authentication when a token is
available, improving consistency and reducing rate-limit risk.
- Repository star and agent-skill loading continues to work gracefully
without token access.

- **Chores**
- Streamlined the type-check workflow to use a leaner content build
before running TypeScript checks.
- Passed the GitHub token through relevant CI task environments to
enable authenticated requests.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

.github/workflows/typecheck.yml

@@ -42,6 +42,8 @@ jobs:
 
       - name: Run TypeScript type check
         run: pnpm run typecheck
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Run Lint
         run: pnpm run lint