fix: add macOS Homebrew Opus fallback and fix shutdown dict iteration

- Add Homebrew library path fallback when ctypes.util.find_library fails
  on macOS (Apple Silicon + Intel paths, guarded by platform check)
- Fix RuntimeError in gateway stop() by iterating over dict copy
- Update Opus tests to verify find_library-first + conditional fallback

gateway/platforms/discord.py

@@ -409,6 +409,19 @@ class DiscordAdapter(BasePlatformAdapter):
         if not discord.opus.is_loaded():
             import ctypes.util
             opus_path = ctypes.util.find_library("opus")
+            # ctypes.util.find_library fails on macOS with Homebrew-installed libs,
+            # so fall back to known Homebrew paths if needed.
+            if not opus_path:
+                import sys
+                _homebrew_paths = (
+                    "/opt/homebrew/lib/libopus.dylib",  # Apple Silicon
+                    "/usr/local/lib/libopus.dylib",     # Intel Mac
+                )
+                if sys.platform == "darwin":
+                    for _hp in _homebrew_paths:
+                        if os.path.isfile(_hp):
+                            opus_path = _hp
+                            break
             if opus_path:
                 try:
                     discord.opus.load_opus(opus_path)

gateway/run.py

@@ -754,7 +754,7 @@ class GatewayRunner:
         logger.info("Stopping gateway...")
         self._running = False
         
-        for platform, adapter in self.adapters.items():
+        for platform, adapter in list(self.adapters.items()):
             try:
                 await adapter.disconnect()
                 logger.info("✓ %s disconnected", platform.value)