docs(discovery): mark the command shapes documented, not observed (t62 nit c)

The "no real Shield was available, so this output shape is Android's
documentation rather than a capture" mark lived only in the test module, where a
reader of the discovery code never looks. It now sits in the module docstring
next to the commands it qualifies, and in the README's app-discovery section
next to the command table, matching the state=6 buffering inference mark in the
source ladder.

custom_components/nvidia_shield/ha_adb_common/installed_apps.py

@@ -5,6 +5,13 @@ fallback list: only four packages were ever offered, so a user with Wholphin,
 SmartTube, Kodi, Plex or anything else saw nothing. The device knows its own
 apps, so this module asks it.
 
+MARK — documented, not observed: the command SHAPES below are Android's own
+documentation, not a captured run. No real Shield was available when this was
+written (t57), so every fixture in ``tests/test_installed_apps.py`` is built from
+those documented shapes, and the parsers are deliberately tolerant of whitespace
+and ordering. This is the same "inferred, not observed" mark the ``state=6``
+buffering value carries in ``media_player.py``.
+
 The commands (both plain `pm`, available on Shield Experience 9 / Android 11
 with no extra permission beyond the ADB pairing this integration already has):