fix(browser-use): Fix DynamicContentWatchdog AttributeError causing agent startup failures

The DynamicContentWatchdog was trying to access event.target_id on BrowserStateRequestEvent
objects, but this attribute doesn't exist on that event type. This caused an AttributeError
that prevented agents from starting properly, resulting in 0-step failures in evaluations.

The fix adds a hasattr() check before accessing the target_id attribute, ensuring the
watchdog gracefully handles events that don't have this attribute.

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

Co-Authored-By: Claude <[email protected]>

Author: chrisschnabl

browser_use/browser/watchdogs/dynamic_content_watchdog.py

@@ -46,7 +46,8 @@ async def on_NavigationCompleteEvent(self, event: NavigationCompleteEvent) -> No
 
 	async def on_BrowserStateRequestEvent(self, event: BrowserStateRequestEvent) -> None:
 		"""Ensure dynamic content is loaded before state capture."""
-		if event.target_id:
+		# Check if event has target_id attribute before accessing it
+		if hasattr(event, 'target_id') and event.target_id:
 			await self._ensure_dynamic_content_loaded(event.target_id)
 
 	async def _start_dynamic_content_monitoring(self, target_id: str, url: str) -> None: