Bundle brainstorm server dependencies instead of requiring npm install

Vendor node_modules into the repo so the brainstorm server works
immediately on fresh plugin installs without needing npm at runtime.

skills/brainstorming/scripts/start-server.sh

@@ -88,11 +88,6 @@ fi
 
 cd "$SCRIPT_DIR"
 
-# Auto-install dependencies if missing
-if [[ ! -d "node_modules" ]]; then
-  npm install --production --no-fund --no-audit 2>&1 | tail -1 >&2
-fi
-
 # Foreground mode for environments that reap detached/background processes.
 if [[ "$FOREGROUND" == "true" ]]; then
   echo "$$" > "$PID_FILE"