fix: let extra bots see peer music state for !similar/!tags

_current_meta now checks registry._bots for peer bot music state
when the current bot has nothing playing. Fixes merlin reporting
"Nothing playing" while derp is actively streaming.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_lastfm.py

@@ -307,6 +307,31 @@ class TestCurrentMeta:
         }
         assert _mod._current_meta(bot) == ("Tool", "Lateralus")
 
+    def test_peer_bot_music_state(self):
+        """Extra bot sees music state from peer bot via shared registry."""
+        music_bot = _FakeBot()
+        music_bot._pstate["music"] = {
+            "current": _FakeTrack(title="Tool - Lateralus"),
+        }
+        extra_bot = _FakeBot()
+        # No music state on extra_bot
+        # Share registry with _bots index
+        shared_reg = _FakeRegistry()
+        shared_reg._bots = {"derp": music_bot, "merlin": extra_bot}
+        music_bot.registry = shared_reg
+        extra_bot.registry = shared_reg
+        assert _mod._current_meta(extra_bot) == ("Tool", "Lateralus")
+
+    def test_peer_bot_no_music(self):
+        """Returns empty when no bot has music state."""
+        bot_a = _FakeBot()
+        bot_b = _FakeBot()
+        shared_reg = _FakeRegistry()
+        shared_reg._bots = {"a": bot_a, "b": bot_b}
+        bot_a.registry = shared_reg
+        bot_b.registry = shared_reg
+        assert _mod._current_meta(bot_a) == ("", "")
+
 
 # ---------------------------------------------------------------------------
 # TestFmtMatch