Fix Pages PR Preview comment permissions

[Copilot]

The Pages PR Preview / deploy (pull_request) job failed after successfully uploading the preview artifact because the PR comment step lacked the required token scope and ran on forked PRs where comments are not writable.

• Workflow permissions

  • Replace pull-requests: write with issues: write, matching the issues.createComment API used by actions/github-script.

• Fork PR handling

  • Run the preview artifact comment only for same-repository PRs.
  • Forked PRs can still build/upload the artifact without failing on the comment step.

permissions:
  pages: write
  id-token: write
  contents: read
  issues: write

# ...
if: github.event_name == 'pull_request' && github.event.pull_request.head.repo.full_name == github.repository