refactor: make Node.js installation automatic in setup.sh

- setup.sh now automatically installs Node 22 via NodeSource if not found
- No more separate manual Node installation step required
- Simplified to single command: bash scripts/setup.sh
- Works for apt/pacman/brew systems
- Updated SETUP_GUIDE.md with simplified instructions
- Better logging during Node installation process

Users can now simply run:
  bash scripts/setup.sh

And everything (including Node 22) will be installed automatically.

scripts/setup.sh

@@ -268,9 +268,10 @@ if has node; then
   if [ "$NODE_MAJOR" = "22" ]; then
     skip "node v$NODE_VER (system-wide)"
   else
-    warn "Node $NODE_VER found but v22 is required — upgrading via NodeSource..."
+    warn "Node $NODE_VER found but v22 is required — upgrading..."
     case $PM in
       apt)
+        echo "  Setting up NodeSource repository..."
         curl -fsSL https://deb.nodesource.com/setup_22.x | sudo -E bash -
         sudo apt-get install -y nodejs
         if has node && [ "$(node -v | cut -d. -f1 | tr -d 'v')" = "22" ]; then
@@ -279,26 +280,40 @@ if has node; then
           fail "Node.js upgrade failed"
         fi
         ;;
-      *)
-        warn "Manual upgrade needed for $PM: install Node.js 22 from official sources"
+      pacman)
+        install_pkg nodejs npm
+        if has node; then ok "node v$(node -v) installed"; else fail "node install failed"; fi
+        ;;
+      brew)
+        install_pkg node
+        if has node; then ok "node v$(node -v) installed"; else fail "node install failed"; fi
         ;;
     esac
   fi
 else
-  warn "Node.js not found — installing v22 via NodeSource..."
+  echo "  Node.js not found — installing v22..."
   case $PM in
     apt)
+      echo "    Setting up NodeSource repository (this may take a moment)..."
       curl -fsSL https://deb.nodesource.com/setup_22.x | sudo -E bash -
+      echo "    Installing nodejs from apt..."
       sudo apt-get install -y nodejs
-      if has node; then ok "node v$(node -v) installed"; else fail "node install failed"; fi
+      if has node; then 
+        ok "node v$(node -v) installed from NodeSource"
+      else 
+        fail "Node.js install failed"
+        exit 1
+      fi
       ;;
     pacman)
+      echo "    Installing nodejs from pacman..."
       install_pkg nodejs npm
-      if has node; then ok "node v$(node -v) installed"; else fail "node install failed"; fi
+      if has node; then ok "node v$(node -v) installed"; else fail "node install failed"; exit 1; fi
       ;;
     brew)
+      echo "    Installing node from brew..."
       install_pkg node
-      if has node; then ok "node v$(node -v) installed"; else fail "node install failed"; fi
+      if has node; then ok "node v$(node -v) installed"; else fail "node install failed"; exit 1; fi
       ;;
   esac
 fi