feat: 24 - Add comprehensive evals for tdd-workflow skill

[miroslavpojer]

Description

This PR establishes a complete eval suite for the tdd-workflow skill, enabling rigorous testing of TDD workflow triggering and body execution across multiple scenarios.

What's included:

• evals/evals.json: 9 eval cases covering happy-path (implement function, fix bug, new class), regressions (no code before confirmation, no private member access), edge cases (existing SPEC.md), output format validation, negative cases, and paraphrased triggers
• evals/trigger-eval.json: 15 trigger validation cases (11 should-trigger, 4 should-not-trigger) verifying the skill activates on explicit TDD requests, implicit code-writing intent, and programmatic variations, while correctly ignoring conceptual questions and pure refactors
• evals/files/bank-account-spec.md: Fixture SPEC.md used by the private-member-access regression eval to ensure tests interact only with public interfaces

Testing approach:

• Happy-path evals verify core TDD sequence: SPEC creation → test table proposal → user confirmation → failing tests → implementation → refactoring
• Regression evals enforce TDD constraints: no coding before confirmation, no private member access in tests
• Trigger evals validate skill activation boundaries on paraphrases and edge cases
• Edge cases test behavior when SPEC.md already exists

Next steps:
Run eval suite via Copilot CLI (gh copilot + Use the skill-creator skill to test my skill at skills/tdd-workflow) to measure trigger accuracy and body output quality against baseline.

Closes #24

[tmikula-dev]

I have used a TDD skill in the past, that is well rated (144k of stars): https://github.com/mattpocock/skills/tree/main/skills/engineering/tdd. The author (@
mattpocock) is the same, that created for example grill-with-docs skill and this TDD skill is regularly updated (last update a week ago). Worth considering.

[miroslavpojer]

I have used a TDD skill in the past, that is well rated (144k of stars): https://github.com/mattpocock/skills/tree/main/skills/engineering/tdd. The author (@ mattpocock) is the same, that created for example grill-with-docs skill and this TDD skill is regularly updated (last update a week ago). Worth considering.

I did comparison and current version is hybrid solution - the solution introduce vertical principle for test creation.