docs: add missing docs

ref: N25B-115

src/control_backend/agents/perception/__init__.py

@@ -1,3 +1,8 @@
+"""
+Agents responsible for processing sensory input, such as audio transcription and voice activity
+detection.
+"""
+
 from .transcription_agent.transcription_agent import (
     TranscriptionAgent as TranscriptionAgent,
 )