Adds spec-tdd to Development & Code Tools. A skill that gates AI implementation behind three hook-enforced human review gates (architecture → patterns → tests) before any production code is written. Approved tests are frozen by SHA-256 + skip-marker counts, so the agent can't silently add .skip to pass.

• Real use case: built to stop agent-written code from drifting off-plan and weakening its own tests.
• Not a duplicate of the existing test-driven-development entry — this is spec-driven with enforced gates + frozen tests, not just a TDD prompt.
• MIT, cross-platform (hooks run via node).

Repo: https://github.com/HagonChan/spec-tdd