ci: add stale branch cleanup workflow

[VdustR]

Summary

• Add a daily GitHub Actions workflow to automatically delete remote branches inactive for 7+ days
• Uses crs-k/stale-branches@v8.2.2 with pr-check enabled to skip branches with open PRs
• Runs daily at 10:00 AM Taiwan time (2:00 AM UTC) with manual dispatch support

Test plan

• Verify workflow appears in Actions tab
• Trigger manually via workflow_dispatch to confirm it runs successfully

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[gemini-code-assist]

Note

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[changeset-bot]

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Latest commit: 038a51d

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[VdustR]

Checklist Verification Report

#	Item	Category	Result
1	Verify workflow appears in Actions tab	Human	⏳ Post-merge
2	Trigger manually via workflow_dispatch to confirm it runs successfully	Human	⏳ Post-merge

Both items require merge to main first — workflow_dispatch is only available for workflows on the default branch.

Subagent Review Notes

Workflow file looks correct overall. A few observations:

1. issues: write permission — the crs-k/stale-branches action may use this for logging/notifications; kept consistent with the reference implementation
2. days-before-stale: 7 + days-before-delete: 7 — branches are deleted on the same run they're detected as stale (no grace period). This is intentional per the reference config
3. pr-check: true correctly protects branches with open PRs
4. repo-token not needed — uses the default GITHUB_TOKEN from permissions

🤖 Generated with Claude Code