docs(sensor): name where the Current App name chain comes from (t55)

The Current App sensor already resolved through the shared
`resolve_app_name` chain, so the package-id live symptom was never a
missing tier — it was the label path being silenced (fix in the previous
commit). Its docstrings now say so explicitly: `_package` is the app on
screen (protocol push → ADB mResumedActivity → recents as a last resort)
and `native_value` resolves exactly that package's map entry or cached
device label, which is why the label fetch must be driven off it. The
behaviour is unchanged; the comment is what was missing.

custom_components/nvidia_shield/sensor.py

@@ -93,10 +93,13 @@ class NvidiaShieldCurrentAppSensor(NvidiaShieldSensorBase):
         self.async_write_ha_state()
 
     def _package(self) -> str | None:
-        """The raw foreground package from the manager's store (t41).
+        """The raw package of the app that is on screen (t41, t55).
 
         StateStore priority chain (P3-3c): protocol current_app push → ADB
-        mResumedActivity → ADB recents.
+        mResumedActivity (both via ``manager.foreground_app``) → the most
+        recent visible ADB recent task. The recents tier is a last resort for
+        a moment when neither live signal has reported yet; it keeps the
+        sensor from going None while ADB is still warming up.
         """
         manager = self._manager()
         if manager is None:
@@ -117,6 +120,13 @@ class NvidiaShieldCurrentAppSensor(NvidiaShieldSensorBase):
         ``resolve_app_name``: apps map → cached manifest label → the package
         text itself. A bare or unknown package shows its package text rather
         than None, like the media player's app_name.
+
+        This is why ``_package`` must be the CURRENT app and the label fetch
+        must be driven off it (t55): the device-manifest label is resolved on
+        demand for exactly the package passed here, so a live run showing a
+        package id means the label tier never answered — see
+        ``ShieldConnectionManager.app_label`` for the caching rule that makes
+        a miss retry instead of being stamped as an eternal "no label".
         """
         manager = self._manager()
         return resolve_app_name(