improvement: use explicit system npm path to avoid nvm conflicts

- When installing global npm packages, explicitly use /usr/bin/npm
- Falls back to $(which npm) if system npm not found
- Ensures packages go to system location, not nvm location
- Works around nvm PATH interference during setup

scripts/setup.sh

@@ -585,12 +585,18 @@ echo "── npm global packages (system-wide) ──"
 if ! has npm; then
   warn "npm not found — skipping global package installs"
 else
+  # Use explicit path to system npm if available, to avoid nvm conflicts
+  SYSTEM_NPM="/usr/bin/npm"
+  if [ ! -f "$SYSTEM_NPM" ]; then
+    SYSTEM_NPM="$(which npm)"
+  fi
+  
   # Pi (coding agent)
   if has pi; then
     skip "pi (@mariozechner/pi-coding-agent)"
   else
     echo "  Installing pi..."
-    sudo npm install -g @mariozechner/pi-coding-agent
+    sudo "$SYSTEM_NPM" install -g @mariozechner/pi-coding-agent
     if has pi; then ok "pi installed"; else warn "pi install failed"; fi
   fi
 
@@ -616,7 +622,7 @@ else
     skip "claude (@anthropic-ai/claude-code)"
   else
     echo "  Installing claude-code..."
-    sudo npm install -g @anthropic-ai/claude-code
+    sudo "$SYSTEM_NPM" install -g @anthropic-ai/claude-code
     if has claude; then ok "claude-code installed"; else warn "claude-code install failed"; fi
   fi