Add cognitive-squad to community extension catalog (#1870)

- Extension ID: cognitive-squad
- Version: 0.1.0
- Author: Testimonial
- 19-function cognitive agent squad for autonomous pre-code analysis
- 7 core agents, 7 specialists, 4 learning functions, feedback loop
- Requires: spec-kit >=0.3.0, optionally understanding >=3.4.0

Repository: https://github.com/Testimonial/cognitive-squad

Co-authored-by: Ladislav Bihari <ladislav.bihari@statsperform.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>