chore: remove redundant files, fix app:setup symlinks

- Remove antigravity-awesome-skills-5.9.0.tgz (npm pack artifact)
- Remove .DS_Store from tracking
- Stop tracking web-app/public/skills and skills.json (generated by app:setup)
- Add .DS_Store, .ruff_cache, *.tgz, web-app/public/skills to .gitignore
- Fix setup_web.js: use statSync to follow symlinks (fixes ENOTDIR on CLAUDE.md)

Made-with: Cursor

.gitignore

@@ -1,6 +1,11 @@
 node_modules/
 __pycache__/
+.ruff_cache/
 .worktrees/
+.DS_Store
+
+# npm pack artifacts
+antigravity-awesome-skills-*.tgz
 
 walkthrough.md
 .agent/rules/
@@ -29,3 +34,7 @@ scripts/*count*.py
 
 # Optional baseline for legacy JS validator (scripts/validate-skills.js)
 validation-baseline.json
+
+# Web app generated assets (from npm run app:setup)
+web-app/public/skills/
+web-app/public/skills.json