解决issue154中的model_output有换行的问题以及多行文本输出。解决subprocessing编码问题

phone_agent/adb/device.py

@@ -22,9 +22,11 @@ def get_current_app(device_id: str | None = None) -> str:
     adb_prefix = _get_adb_prefix(device_id)
 
     result = subprocess.run(
-        adb_prefix + ["shell", "dumpsys", "window"], capture_output=True, text=True
+        adb_prefix + ["shell", "dumpsys", "window"], capture_output=True, text=True, encoding="utf-8"
     )
     output = result.stdout
+    if not output:
+        raise ValueError("No output from dumpsys window")
 
     # Parse window focus info
     for line in output.split("\n"):