Claude Code TDD Loop: Red, Green, Refactor Done Right

Forces Claude Code through a strict red→green→refactor cycle: for every behavior, first write a test that fails (red) and actually run it to prove the failure, then write the minimal implementation that just makes it pass (green), and finally refactor under the safety of the passing tests. Cures the AI's old habit of jumping straight to the happy path, skipping edge cases, and faking test coverage.