refactor(vscode-ide-companion): clean up code and improve type safety

- Remove commented out error handling code in acpMessageHandler
- Simplify session update handler by removing redundant comments
- Clean up chat types interface definitions
- Simplify null check in MessageRouter
- Improve type safety in SettingsMessageHandler with ApprovalModeValue type

packages/vscode-ide-companion/src/webview/handlers/MessageRouter.ts

@@ -150,13 +150,7 @@ export class MessageRouter {
    */
   setLoginHandler(handler: () => Promise<void>): void {
     this.authHandler.setLoginHandler(handler);
-    // Also set login handler for SessionMessageHandler
-    if (
-      this.sessionHandler &&
-      typeof this.sessionHandler.setLoginHandler === 'function'
-    ) {
-      this.sessionHandler.setLoginHandler(handler);
-    }
+    this.sessionHandler?.setLoginHandler?.(handler);
   }
 
   /**