chore: migrate to pnpm v11, switch to nano-staged, add skills-npm

- Bump packageManager to pnpm@11.1.3; rename onlyBuiltDependencies to allowBuilds
- Replace lint-staged with nano-staged
- Add skills-npm via prepare chain
- Set core.hooksPath to .githooks so simple-git-hooks works in worktrees

.gitignore

@@ -1,5 +1,6 @@
 .cache
 .DS_Store
+.githooks
 .idea
 *.log
 *.tgz
@@ -8,4 +9,5 @@ dist
 lib-cov
 logs
 node_modules
+skills/npm-*
 temp