Review fixes: logoff inventory, socket stop, connect order, relog leftovers

F2: the logoff inventory is skipped when the host already let go of the
items (it may reset the session before reporting the logoff): an empty list
would have emptied the backend's inventory and overwritten the saved copy.
F3/F4: each socket start owns its run; Stop no longer blocks the game thread
and gives the run up to ten seconds to send what was queued (a large logoff
inventory) before closing, flushing that run's own send loop; a relog never
hears the previous run's frames.
F7: on connect, share_subscribe goes out before the first telemetry frame, as
the original sent them.
F8: a rare announcement still waiting at logoff is dropped rather than sent
as the next character.
F9: each dungeon map is sent once per login, as the original (reloaded per
login) did.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/OpenAC.MosswartMassacre/Radar/RadarStream.cs

@@ -50,9 +50,7 @@ internal sealed class RadarStream : IMmFeature
         _context.Verbose("[Radar] Stopped nearby objects tracker");
     }
 
-    public void OnLogin()
-    {
-    }
+    public void OnLogin() => _mapsSent.Clear();
 
     public void OnLogoff() => Stop();