Fix stereo speakers pair unsync

app.py

@@ -217,10 +217,20 @@ def _spotify_release(key: str, account: str = None) -> dict:
     intact. Putting the speaker on one of its own inputs does end the
     stream, and stopping *that* is honoured, so the room is left idle
     rather than sitting on a live input.
+
+    A stereo pair is the exception: it gets the pause and nothing more.
+    Signing out restarts the leader's receiver, and a leader restarted that
+    way can come back playing alone -- the other half silent until the pair
+    is power-cycled. The Spotify app never signs a speaker out, which is
+    why it never trips over this. Left signed in, the pair is still either
+    button's to claim: a sign-in moves it between accounts regardless.
     """
-    released = {"paused": _spotify_pause_on(key, account), "signed_out": False}
+    released = {"paused": _spotify_pause_on(key, account), "signed_out": False, "paired": False}
     speaker = None if _is_demo() else _find_speaker(_spotify_name(key))
     if speaker is not None:
+        if _is_paired(speaker):
+            released["paired"] = True
+            return released
         speaker.reset_users()
         released["signed_out"] = True
         return released
@@ -228,6 +238,16 @@ def _spotify_release(key: str, account: str = None) -> dict:
     return released
 
 
+def _is_paired(speaker) -> bool:
+    """Whether the receiver is one half of a stereo pair (or any In-Room
+    Group) -- getInfo's groupStatus says GROUP, where a lone speaker says
+    NONE. One that will not say is treated as alone, as before."""
+    try:
+        return speaker.info().get("groupStatus") == "GROUP"
+    except ZeroconfError:
+        return False
+
+
 def _release_over_heos(key: str):
     """Stop a room's Spotify stream without the speaker's help -- see
     _spotify_release for why it goes the long way round."""

static/app.js

@@ -794,9 +794,13 @@ async function disconnectSpotify(button) {
     // The speaker not answering on the LAN is not a failure -- the room
     // still stops -- but it does leave the account signed in to it, and
     // that is the difference between "let go of" and "stopped".
+    // A stereo pair is only ever paused -- signing it out can leave one
+    // half silent -- so it staying signed in is the plan, not a failure.
     toast(data.signed_out
       ? `${data.device} let go of ${who}'s Spotify`
-      : `Stopped ${who}'s Spotify on ${data.device} — the speaker did not answer, so it stays signed in`,
+      : data.paired
+        ? `Paused ${who}'s Spotify on ${data.device}`
+        : `Stopped ${who}'s Spotify on ${data.device} — the speaker did not answer, so it stays signed in`,
       'ok');
     // The room stops with it, so drop the border, the transport row and the
     // song now rather than leaving a card that still claims to be playing;