Stabilize GitHub Pages deploy by replacing dynamic workflow with explicit Pages pipeline

[Copilot]

The failing deploy job timed out while actions/deploy-pages@v5 remained in deployment_queued until the default 10-minute action timeout was reached. This change makes the Pages deployment path explicit and resilient to queue latency.

• Root-cause alignment

  • Replaces reliance on the generated/dynamic Pages workflow with a repository-owned workflow so deploy behavior is configurable in-repo.

• Pages workflow added

  • Introduces .github/workflows/pages.yml with standard Pages stages:
    • actions/checkout@v4
    • actions/configure-pages@v5
    • actions/upload-pages-artifact@v4 (root path)
    • actions/deploy-pages@v5

• Deploy timeout and queue handling

  • Increases deploy action timeout to 30 minutes to tolerate Pages-side queueing.
  • Adds workflow-level concurrency (group: pages, cancel-in-progress: true) to avoid stale overlapping deploy attempts.

deploy:
  needs: build
  steps:
    - name: Deploy to GitHub Pages
      id: deployment
      uses: actions/deploy-pages@v5
      with:
        timeout: 1800000