feat(claude): add derive-commit-taxonomy skill for designing a repo's commit taxonomy

[ppat]

What

Adds private_dot_claude/skills/derive-commit-taxonomy/SKILL.md — a skill that guides an LLM through deriving a commit type/scope taxonomy for a repository it has not seen, plus the enforcement, rule document, and verification that make the taxonomy real.

Why a method, not an answer

No two repos will look the same (especially for scopes): of the two repos this method has been applied to (github-workflows, homelab-ops-kubernetes-apps), the type enums converged but the scope enums share almost nothing. The skill therefore deliberately carries no default enum — it teaches:

• The questions, in order: what routes a release; what reads each header field and does anything act on it; whether the gate is actually enforced on what lands; what the bot can emit and whether the gate would accept it; which scopes the release layer knows about; what a shared-preset bump does to emission.
• The traps (the part that took two adversarial review rounds to find): enforcement decomposes per actor and per merge path; a check the dominant actor cannot satisfy is not a check; equivalence classes leak repo state; verify the verifier's own scope; and the calver lesson — an adversarial pass can manufacture a defect by judging a rule against a prior that does not govern the artifact.
• A three-layer verification shape (closure by construction / runtime gate + declared sampling / falsification with injected defects), including why a raw cross-product and a purely analytic config reading each failed on their own.
• How to write the resulting rule document so a future session can decide from the diff alone.

The skill states its sample size (two repos) and ends with an amendment protocol: extend it after each repo it is applied to, per the intent that it improves iteratively as overriding patterns emerge.

🤖 Generated with Claude Code