feat: add browser configuration tool and fix STDIO mode

- Add browser_configure tool to change headless/headed mode, viewport, and user agent during session
- Fix STDIO entry point by preventing stdin close handlers in STDIO mode
- Fix headed mode default behavior when DISPLAY is available on Linux
- Add dynamic browser configuration update mechanism in Context class

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/tools.ts

@@ -15,6 +15,7 @@
  */
 
 import common from './tools/common.js';
+import configure from './tools/configure.js';
 import console from './tools/console.js';
 import dialogs from './tools/dialogs.js';
 import evaluate from './tools/evaluate.js';
@@ -36,6 +37,7 @@ import type { FullConfig } from './config.js';
 
 export const allTools: Tool<any>[] = [
   ...common,
+  ...configure,
   ...console,
   ...dialogs,
   ...evaluate,