Fix weekly duplication reporting workflow

[aaronpowell]

Summary

The scheduled weekly duplication report workflow is not producing reliable output.

Workflow links

• Workflow definition: https://github.com/github/awesome-copilot/blob/staged/.github/workflows/duplicate-resource-detector.md
• GitHub run list: https://github.com/github/awesome-copilot/actions/workflows/duplicate-resource-detector.lock.yml

Scope

• Identify why scheduled execution/report generation is failing
• Fix workflow steps, permissions, and/or query logic as required
• Validate report output shape and expected recipients/targets
• Update documentation for schedule/config behavior if changed

Acceptance criteria

• Weekly workflow runs successfully on schedule (or manual trigger in equivalent path)
• Report output is generated and includes expected sections
• No blocking runtime/auth/config errors remain
• Documentation reflects the current behavior

Parent

Part of #2076