feat: add brainstorm server foundation

Create the initial server for the visual brainstorming companion:
- Express server with WebSocket support for browser communication
- File watcher (chokidar) to detect screen.html changes
- Auto-injects helper.js into served HTML for event capture
- Binds to localhost only (127.0.0.1) for security
- Outputs JSON events to stdout for Claude consumption

lib/brainstorm-server/package.json

@@ -0,0 +1,11 @@
+{
+  "name": "brainstorm-server",
+  "version": "1.0.0",
+  "description": "Visual brainstorming companion server for Claude Code",
+  "main": "index.js",
+  "dependencies": {
+    "chokidar": "^3.5.3",
+    "express": "^4.18.2",
+    "ws": "^8.14.2"
+  }
+}