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

driver/base.py

@@ -3,6 +3,8 @@ from __future__ import annotations
 from abc import ABC, abstractmethod
 from typing import Any
 
+from core.models import ActiveApp
+
 
 class Driver(ABC):
     """Driver-independent device capability interface.
@@ -71,6 +73,10 @@ class Driver(ABC):
     def tree(self) -> Any:
         """Return the raw UI tree from the device driver."""
 
+    def active_app(self) -> ActiveApp | None:
+        """Return foreground application metadata when the driver supports it."""
+        return None
+
     @abstractmethod
     def home(self) -> None:
         """Press the device home button."""
@@ -82,4 +88,3 @@ class Driver(ABC):
     @abstractmethod
     def unlock(self) -> None:
         """Unlock the device."""
-