refactor: auto-discover channels via pkgutil, eliminate hardcoded registry

nanobot/channels/base.py

@@ -1,6 +1,9 @@
 """Base channel interface for chat platforms."""
 
+from __future__ import annotations
+
 from abc import ABC, abstractmethod
+from pathlib import Path
 from typing import Any
 
 from loguru import logger
@@ -18,6 +21,8 @@ class BaseChannel(ABC):
     """
 
     name: str = "base"
+    display_name: str = "Base"
+    transcription_api_key: str = ""
 
     def __init__(self, config: Any, bus: MessageBus):
         """
@@ -31,6 +36,19 @@ class BaseChannel(ABC):
         self.bus = bus
         self._running = False
 
+    async def transcribe_audio(self, file_path: str | Path) -> str:
+        """Transcribe an audio file via Groq Whisper. Returns empty string on failure."""
+        if not self.transcription_api_key:
+            return ""
+        try:
+            from nanobot.providers.transcription import GroqTranscriptionProvider
+
+            provider = GroqTranscriptionProvider(api_key=self.transcription_api_key)
+            return await provider.transcribe(file_path)
+        except Exception as e:
+            logger.warning("{}: audio transcription failed: {}", self.name, e)
+            return ""
+
     @abstractmethod
     async def start(self) -> None:
         """