feat(perception): expose active app metadata in UI tree

driver/android_driver.py

@@ -5,6 +5,7 @@ from dataclasses import dataclass, field
 from typing import Any
 
 from core.errors import DeviceOfflineError, DriverError
+from core.models import ActiveApp
 from driver.base import Driver
 
 # Android KeyEvent.KEYCODE_HOME. Kept as a literal rather than importing the
@@ -170,6 +171,19 @@ class AndroidDriver(Driver):
         except Exception as exc:
             raise DriverError("ui tree retrieval failed") from exc
 
+    def active_app(self) -> ActiveApp | None:
+        client = self._require_client()
+        try:
+            package = client.current_package
+            activity = client.current_activity
+        except Exception as exc:
+            raise DriverError("active app retrieval failed") from exc
+        package = package if isinstance(package, str) and package else None
+        activity = activity if isinstance(activity, str) and activity else None
+        if package is None and activity is None:
+            return None
+        return ActiveApp(platform="android", package=package, activity=activity)
+
     def home(self) -> None:
         client = self._require_client()
         try: