fix: declare undeclared soft deps in extras and remove silent import guards

Previously mutagen, aiohttp-socks, tiktoken, Pillow, psutil, datasets,
neutts, and soundfile were used behind try/except ImportError with silent
fallbacks, masking broken functionality at runtime.  Declare each in its
natural extra (messaging, cli, mcp, rl, new tts-local) so they get
installed, and remove the guards so missing deps crash loudly.

gateway/platforms/discord.py

@@ -1194,9 +1194,10 @@ class DiscordAdapter(BasePlatformAdapter):
             try:
                 import base64
 
+                from mutagen.oggopus import OggOpus
+
                 duration_secs = 5.0
                 try:
-                    from mutagen.oggopus import OggOpus
                     info = OggOpus(audio_path)
                     duration_secs = info.info.length
                 except Exception: