ci: add Phase 1 CI workflow

[jcameronjeff]

Phase 1 CI for skillz — adds .github/workflows/ci.yml (additive new file). Part of the org-wide CI/CD formalization; deploys unchanged.

Prerequisites

Cautions

• Verified against current repo: 5 skills (deploy-to-opzero, multi-cloud-deploy, opzero-mcp-setup, opzero-quick-start, static-site-best-practices), all with valid frontmatter where name == dir name, and README table matches disk. CI should pass as-is on first run.
• Directory note: org-profile docs call this repo 'skills/' but the actual cloned/remote dir is 'skillz/'. The repo's own internal layout uses skills//SKILL.md, which is what the workflow validates — unaffected by the top-level dir rename.
• The README drift check keys off markdown links of the form ](skills//SKILL.md). If the README table format changes (e.g. links dropped), the drift check will report false positives — keep the table linking each skill to its SKILL.md.
• PyYAML is pinned (6.0.2) and installed from PyPI at CI time; this is the only network dependency. No lockfile is committed because the repo has no Node/Bun package — this is expected for a markdown repo, not a gap.

Generated with Claude Code

https://claude.ai/code/session_01XD3eqvjHj4QckgL2iuj47u