Add AutoTriage workflows for label-only issue and PR triage

[Copilot]

Adds AutoTriage for newly opened issues and pull requests using the MudBlazor setup as the reference point. The configuration is constrained to apply DesktopClock’s standard labels only, with no comments, title edits, or state changes.

• Workflows

  • Added issue triage workflow for issues.opened
  • Added PR triage workflow for pull_request_target on opened and ready_for_review
  • Configured both workflows to skip the fast model and use gemini-3.1-flash-lite-preview as the review model

• Triage policy

  • Added a repo-specific .github/AutoTriage.prompt
  • Restricted AutoTriage actions to label application only
  • Scoped labeling to the repository’s standard labels: bug, enhancement, question, invalid, plus clearly-supported secondary labels such as duplicate, wontfix, help wanted, and good first issue

• Operational details

  • Reused a shared triage DB cache across runs
  • Granted only the permissions needed to read contents and write issue/PR metadata

- name: AutoTriage - triage issue
  uses: danielchalmers/AutoTriage@v3
  with:
    issues: ${{ github.event.issue.number }}
    prompt-path: .github/AutoTriage.prompt
    db-path: triage-db.json
    model-fast: ""
    model-pro: gemini-3.1-flash-lite-preview