fix: clean stale Chromium SingletonLock before launch (crash recovery)

deepseek_browser.py

@@ -56,6 +56,14 @@ class DeepSeekBrowser:
 
     async def start(self):
         self.profile_dir.mkdir(parents=True, exist_ok=True)
+        # Clean up stale Chromium lock files from previous crashes
+        for lock in ["SingletonLock", "SingletonCookie", "SingletonSocket"]:
+            lp = self.profile_dir / lock
+            if lp.exists():
+                try:
+                    lp.unlink()
+                except Exception:
+                    pass
         args = [
             "--disable-gpu", "--disable-dev-shm-usage", "--disable-extensions",
             "--disable-background-networking", "--disable-default-apps",