fix(backend): avoid event loop blocking and treat CDP timeout as success

Use run_in_executor for blocking readline so the event loop stays
responsive during the CDP readiness check. Treat the timeout case
(process alive, CDP slow) as success since the browser window is
already open for the user. Only report failure when the process
actually crashes.

Author: eureka0928

backend/app/controller/tool_controller.py

@@ -50,7 +50,7 @@ async def _wait_for_cdp_ready(
     timeout: float = 10,
     interval: float = 0.3,
 ) -> bool:
-    r"""Poll until CDP port is open or process exits. Returns True if ready."""
+    """Poll until CDP port is open or process exits. Returns True if ready."""
     elapsed = 0.0
     while elapsed < timeout:
         if process.poll() is not None:
@@ -783,11 +783,18 @@ def is_port_in_use(port):
 
         _login_browser_process = process
 
-        # Create async task to log Electron output
+        # Log Electron output in a background task.
+        # readline() is blocking, so run it in an executor
+        # to avoid stalling the event loop.
         async def log_electron_output():
-            for line in iter(process.stdout.readline, ""):
-                if line:
-                    logger.info(f"[ELECTRON OUTPUT] {line.strip()}")
+            loop = asyncio.get_event_loop()
+            while True:
+                line = await loop.run_in_executor(
+                    None, process.stdout.readline
+                )
+                if not line:
+                    break
+                logger.info(f"[ELECTRON OUTPUT] {line.strip()}")
 
         asyncio.create_task(log_electron_output())
 
@@ -810,23 +817,15 @@ async def log_electron_output():
                     " before CDP became ready."
                     f" Exit code: {exit_code}",
                 }
-            else:
-                # Timeout — process is still alive but CDP
-                # port never opened. Keep tracking the process
-                # so /browser/status still reports it.
-                logger.warning(
-                    "[PROFILE USER LOGIN] CDP port"
-                    f" {cdp_port} not ready after"
-                    " timeout, but process"
-                    f" {process.pid} is still running"
-                )
-                return {
-                    "success": False,
-                    "error": "Browser started but CDP"
-                    f" port {cdp_port} did not become"
-                    " available in time.",
-                    "pid": process.pid,
-                }
+            # Timeout — process is alive but CDP port not
+            # ready yet. The browser window is open so the
+            # user can proceed with login.
+            logger.warning(
+                "[PROFILE USER LOGIN] CDP port"
+                f" {cdp_port} not ready after"
+                " timeout, but process"
+                f" {process.pid} is still running"
+            )
 
         logger.info(
             "[PROFILE USER LOGIN] Electron"
@@ -860,7 +859,7 @@ async def log_electron_output():
 
 @router.get("/browser/status", name="browser status")
 async def browser_status():
-    r"""Check if the login browser is still running."""
+    """Check if the login browser is still running."""
     global _login_browser_process
     if _login_browser_process is None:
         return {"is_open": False}