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).

custom_components/nvidia_shield/ha_adb_common/media_session.py

@@ -17,6 +17,12 @@ class MediaSessionInfo:
     **device uptime-ms** timestamp (verified on Shield Android 11, R9), not a
     wallclock value. Use :meth:`position_at_uptime` with the device's current
     uptime to extrapolate the live position.
+
+    ``playing``/``paused``/``buffering`` are independent flags mapped from the
+    Android PlaybackState integer: 2 = paused, 3 = playing, 6 = buffering
+    (t55). The Shield's own ExoPlayer/MediaSession sessions report state 6
+    while buffering just as stock Android does, so no vendor-specific state
+    integer is treated as buffering.
     """
 
     title: str | None = None
@@ -25,6 +31,7 @@ class MediaSessionInfo:
     package: str | None = None
     playing: bool = False
     paused: bool = False
+    buffering: bool = False
     position: float | None = None
     speed: float | None = None
     updated: int | None = None
@@ -81,7 +88,8 @@ def parse_all_media_sessions(dump: str) -> list[MediaSessionInfo]:
     """Parse `dumpsys media_session` output for ALL active media sessions.
 
     Returns a list of every active session that has metadata or a known
-    playback state, sorted: playing first, then paused, then others.
+    playback state, sorted: playing first, then buffering, then paused, then
+    others (t55).
     """
     if not dump:
         return []
@@ -89,7 +97,8 @@ def parse_all_media_sessions(dump: str) -> list[MediaSessionInfo]:
     sessions: list[MediaSessionInfo] = []
     current_pkg: str | None = None
     in_active = False
-    current_state = 0  # 0=unknown, 2=paused, 3=playing
+    # Android PlaybackState: 0=unknown, 2=paused, 3=playing, 6=buffering
+    current_state = 0
     current_position: float | None = None
     current_speed: float | None = None
     current_updated: int | None = None
@@ -138,6 +147,7 @@ def parse_all_media_sessions(dump: str) -> list[MediaSessionInfo]:
             info = MediaSessionInfo()
             info.package = current_pkg
             info.playing = current_state == 3
+            info.buffering = current_state == 6
             info.paused = current_state == 2
             info.position = current_position
             info.speed = current_speed
@@ -158,13 +168,16 @@ def parse_all_media_sessions(dump: str) -> list[MediaSessionInfo]:
         current_meta.package = current_pkg
         sessions.append(current_meta)
 
-    # Sort: playing first, then paused, then others
+    # Sort: playing first, then buffering (mid-playback), then paused, then
+    # others — a buffering session outranks a paused one (t55).
     def sort_key(s: MediaSessionInfo) -> int:
         if s.playing:
             return 0
-        if s.paused:
+        if s.buffering:
             return 1
-        return 2
+        if s.paused:
+            return 2
+        return 3
 
     sessions.sort(key=sort_key)
     return sessions
@@ -206,8 +219,9 @@ def parse_media_session(
     Returns the best match from all active sessions:
     1. The session whose package matches the foreground app (if provided)
     2. The session that is currently playing (state=3)
-    3. The session that is paused (state=2)
-    4. Any active session with metadata
+    3. The session that is buffering (state=6)
+    4. The session that is paused (state=2)
+    5. Any active session with metadata
     """
     sessions = parse_all_media_sessions(dump)
     if not sessions:
@@ -218,6 +232,5 @@ def parse_media_session(
         for s in sessions:
             if s.package == foreground_package:
                 return s
-
-    # Already sorted: playing > paused > other
+    # Already sorted: playing > buffering > paused > other
     return sessions[0]