ci: add sync-skills workflow and rename CLAUDE.md to AGENTS.md

[ko3n1g]

Summary

• Rename CLAUDE.md → AGENTS.md: The agent instructions file is renamed to the canonical AGENTS.md name, recognized by a broader set of AI coding assistants. Pure rename, no content changes.
• Add .github/workflows/sync-skills.yml: A new workflow that automatically creates symlinks on every push to main that touches skills/** or AGENTS.md:
  • skills/ → .claude/skills and .agents/skills
  • AGENTS.md → CLAUDE.md

Background

There is no common standard for markdown file discovery across agent frameworks — each tool looks in a different place. This PR addresses that gap by coupling the generic AGENTS.md / skills/ layout with a sync job that runs on push to main, so every agent runtime finds the files it expects without per-framework duplication.

Example result after the workflow runs

.claude/skills  -> ../skills   (symlink)
.agents/skills  -> ../skills   (symlink)
CLAUDE.md       -> AGENTS.md   (symlink)

Test plan

• Merge this PR; verify the Sync skills → agent dirs workflow triggers and commits the three symlinks to main
• Confirm CLAUDE.md still resolves to the correct content via the symlink
• Manually trigger via workflow_dispatch to validate on demand

🤖 Generated with Claude Code