chore: SOTA audit fixes – catalog recursive, readme regex, docs, CI, installer

- P0: Catalog includes nested skills (listSkillIdsRecursive), 626 skills
- P0: update_readme.py regex fixes 'high-performance agentic skills'
- P1: SKILL_ANATOMY risk values aligned to none|safe|critical|offensive (EN + vi)
- P1: requirements.txt + CONTRIBUTING Python setup
- P1: data/package.json version 4.6.0
- P2: npm run test + CI test step; validator docs + validation-baseline in .gitignore
- P3: Installer --version/--tag support; CI npm audit; __pycache__ in .gitignore

data/package.json

@@ -1,6 +1,6 @@
 {
   "name": "antigravity-awesome-skills",
-  "version": "4.2.0",
+  "version": "4.6.0",
   "dependencies": {
     "yaml": "^2.8.2"
   }