feat: add openclaw-github-repo-commander skill

[wd041216-bit]

Description

Adds openclaw-github-repo-commander — a 7-stage super workflow skill for comprehensive GitHub repository management, cleanup, and optimization.

What this skill does:

• Stage 1–7 workflow: Intake → Execution → Reflection → Competitor Analysis → Synthesis → Iteration → Validation
• • Automated audit: scripts/repo-audit.sh checks for hardcoded secrets, tracked node_modules, empty directories, large files, and broken links
• • Competitor benchmarking: Structured Stage 4 analysis against similar repos
• • Security-first: Scans for common secret patterns, excludes workflow files from false positives
• • Model-agnostic: Works with any GitHub Copilot model

Type of Contribution

• New skill file.

Pull Request Checklist

• I have read and followed the CONTRIBUTING.md guidelines.
• - [x] I have read and followed the Guidance for submissions involving paid services.
• - [x] My contribution adds a new instruction, prompt, agent, skill, or workflow file in the correct directory.
• - [x] The file follows the required naming convention.
• - [x] The content is clearly structured and follows the example format.
• - [x] I have tested my instructions, prompt, agent, skill, or workflow with GitHub Copilot.
• - [x] I have run npm start and verified that README.md is up to date.

Additional Notes

This PR targets the staged branch as required by CONTRIBUTING.md. The docs/README.skills.md has been updated via npm start.