feat(media_session): map Android PlaybackState 6 to buffering (t55)

The media session parser only understood states 2 (paused) and 3
(playing), so a session refilling its buffer (Android state 6, which the
Shield's own ExoPlayer/MediaSession sessions report exactly like stock
Android) read as "idle" or vanished into the foreground tier.

MediaSessionInfo gains an independent `buffering` flag (playing/paused/
buffering are now three flags off one integer), the session sort puts
buffering right behind playing — it is mid-playback, so it outranks a
paused session when the ladder picks one — and the running-apps
enrichment names a buffering live/last-known session "buffering" instead
of falling into "idle".

The MediaPlayerState stub gains BUFFERING and STANDBY so an in-suite
reference to a member real HA does not have fails here (real HA 2026.10
exposes off/on/idle/playing/paused/standby/buffering).

tests/entity_stublib.py

@@ -79,6 +79,8 @@ class MediaPlayerState(enum.StrEnum):
     IDLE = "idle"
     PLAYING = "playing"
     PAUSED = "paused"
+    STANDBY = "standby"
+    BUFFERING = "buffering"
 
 
 class MediaPlayerEntityFeature(enum.IntFlag):

tests/test_media_session.py

@@ -125,6 +125,76 @@ class TestPlaybackStatePosition:
         assert sessions[0].position is None
 
 
+class TestPlaybackStateBufferingT55:
+    """t55: Android PlaybackState 6 is BUFFERING, mapped in the parser.
+
+    The Shield's own sessions report the same integer stock Android does (6),
+    so no vendor-specific variant is treated as buffering — a device variant
+    would be a template field on the same PlaybackState line, never a
+    different integer.
+    """
+
+    def _buffering_dump(self, state=6, speed="0.0"):
+        return (
+            "Sessions Stack - have 1 sessions:\n"
+            "  Some app session com.netflix.ninja/Session (userId=0)\n"
+            "    package=com.netflix.ninja\n"
+            "    active=true\n"
+            f"    state=PlaybackState {{state={state}, position=0, "
+            f"buffered position=2000, speed={speed}, updated=900, actions=1, "
+            "custom actions=[], active item id=0, error=null}\n"
+            "    metadata: size=2, description=Movie Title, Some Artist\n"
+        )
+
+    def test_state_6_is_buffering(self):
+        sessions = parse_all_media_sessions(self._buffering_dump())
+        assert len(sessions) == 1
+        session = sessions[0]
+        assert session.buffering is True
+        assert session.playing is False
+        assert session.paused is False
+        assert session.title == "Movie Title"
+
+    def test_state_3_and_2_stay_playing_and_paused(self):
+        for state, attr in ((3, "playing"), (2, "paused")):
+            sessions = parse_all_media_sessions(self._buffering_dump(state=state))
+            session = sessions[0]
+            assert session.buffering is False
+            assert getattr(session, attr) is True
+
+    def test_state_6_wins_when_the_dump_says_speed_zero_too(self):
+        """The buffering signal is the integer, not the speed field."""
+        sessions = parse_all_media_sessions(self._buffering_dump(state=6))
+        assert sessions[0].buffering is True
+
+    def test_buffering_outranks_a_paused_session_in_the_pick_order(self):
+        sessions = parse_all_media_sessions(
+            self._buffering_dump()
+            + "  Other app session com.example.player/Session (userId=0)\n"
+            "    package=com.example.player\n"
+            "    active=true\n"
+            "    state=PlaybackState {state=2, position=1, speed=0.0, "
+            "updated=1, actions=1, custom actions=[], active item id=0, "
+            "error=null}\n"
+            "    metadata: size=1, description=Paused Tune\n"
+        )
+        assert [s.package for s in sessions] == [
+            "com.netflix.ninja",
+            "com.example.player",
+        ]
+        # and parse_media_session (no foreground preference) picks buffering
+        dump = self._buffering_dump() + (
+            "  Other app session com.example.player/Session (userId=0)\n"
+            "    package=com.example.player\n"
+            "    active=true\n"
+            "    state=PlaybackState {state=2, position=1, speed=0.0, "
+            "updated=1, actions=1, custom actions=[], active item id=0, "
+            "error=null}\n"
+            "    metadata: size=1, description=Paused Tune\n"
+        )
+        assert parse_media_session(dump).package == "com.netflix.ninja"
+
+
 class TestAudioPlaybackSection:
     """The "Audio playback (lastly played comes first)" section lists apps
     that recently played audio even with no MediaSession (R2)."""
@@ -160,6 +230,29 @@ class TestAudioPlaybackSection:
         assert parse_audio_playback("") == []
 
 
+def test_running_apps_buffering_state_t55():
+    """t55: a buffering session (and a buffering last-known) is named buffering."""
+    from nsh.ha_adb_common import MediaSessionInfo, running_apps_from_tasks
+
+    tasks = [
+        {"package": "com.netflix.ninja"},
+        {"package": "ar.tvplayer.tv"},
+    ]
+    sessions = [MediaSessionInfo(package="com.netflix.ninja", buffering=True)]
+    last_known = {
+        "ar.tvplayer.tv": MediaSessionInfo(package="ar.tvplayer.tv", buffering=True)
+    }
+
+    apps = running_apps_from_tasks(
+        tasks, sessions, foreground_package=None, last_known=last_known
+    )
+
+    netflix = next(a for a in apps if a["package"] == "com.netflix.ninja")
+    tivi = next(a for a in apps if a["package"] == "ar.tvplayer.tv")
+    assert netflix["state"] == "buffering"
+    assert tivi["last_known_state"] == "buffering"
+
+
 def test_running_apps_last_known_enrichment():
     """P3-3b: apps without a live session carry their TTL-capped last-known state."""
     from nsh.ha_adb_common import MediaSessionInfo, running_apps_from_tasks