fix: use homebrew node instead of nix read-only nodejs

- nodejs from nixpkgs is read-only, breaks pi-coding-agent internal npm install
- Use homebrew node (writable) for proper npm/pnpm global installs
- Remove pi-node hardcoded path hack from PATH

home/cli.nix

@@ -20,7 +20,7 @@
     micro
 
     # Node.js ecosystem
-    nodejs          # runtime for pi-coding-agent and other JS tools
+    # nodejs # read-only в nix store не подходит для pi (npm install ломается)
     pnpm            # fast node package manager
 
     # Secrets