Implement authenticate/update message handling for Qwen OAuth authentication

- Added authenticate_update method to ACP schema constants
- Added AuthenticateUpdateNotification type definitions
- Updated ACP message handler to process authenticate/update notifications
- Added VS Code notification handler with 'Open in Browser' and 'Copy Link' options
- Integrated authenticate update handling in QwenAgentManager

This implementation allows users to easily authenticate with Qwen OAuth when automatic browser launch fails by providing a notification with direct link and copy functionality.

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

packages/vscode-ide-companion/src/services/acpMessageHandler.ts

@@ -17,6 +17,7 @@ import type {
   AcpResponse,
   AcpSessionUpdate,
   AcpPermissionRequest,
+  AuthenticateUpdateNotification,
 } from '../types/acpTypes.js';
 import { CLIENT_METHODS } from '../constants/acpSchema.js';
 import type {
@@ -168,6 +169,15 @@ export class AcpMessageHandler {
         );
         callbacks.onSessionUpdate(params as AcpSessionUpdate);
         break;
+      case CLIENT_METHODS.authenticate_update:
+        console.log(
+          '[ACP] >>> Processing authenticate_update:',
+          JSON.stringify(params).substring(0, 300),
+        );
+        callbacks.onAuthenticateUpdate(
+          params as AuthenticateUpdateNotification,
+        );
+        break;
       case CLIENT_METHODS.session_request_permission:
         result = await this.handlePermissionRequest(
           params as AcpPermissionRequest,