Chore: Implement Automated Snippet Validation Script for CI

[EndlessTrax]

Problem

The current validation in GitHub Actions parses snippet files as JSON inline via node -e. We should make this more robust and run it as a regular npm test script.

Solution

1. Add a validation script at scripts/validate-snippets.js that checks for:
   • Valid JSON formatting.
   • All snippets containing prefix, body, and description.
   • Prefix naming convention (pt prefix).
   • Duplicate prefixes across catalogs to avoid collisions.
2. Update package.json with a test script: "test": "node scripts/validate-snippets.js".
3. Update GitHub Actions config ci.yml to run npm test instead of inline script.