Add spec-validate to community catalog (#2274)

* Add spec-validate to community catalog

- Extension ID: spec-validate
- Version: 1.0.1
- Author: Ahmed Eltayeb
- Description: Comprehension validation, review gating, and approval state for spec-kit artifacts

* Reorder spec-validate before speckit-utils (address Copilot feedback)

Lexicographically 'spec-validate' < 'speckit-utils' because '-' (0x2D)
sorts before 'k' (0x6B). Move the entry to match the alphabetical
ordering used in the 's' range of the catalog.