feat: experiment log stream, to file and UI

Adds a few new logging utility classes. One to save to files with a date, one to support optional fields in formats, last to filter partial log messages.

ref: N25B-401

src/control_backend/agents/base.py

@@ -1,9 +1,10 @@
 import logging
+from abc import ABC
 
 from control_backend.core.agent_system import BaseAgent as CoreBaseAgent
 
 
-class BaseAgent(CoreBaseAgent):
+class BaseAgent(CoreBaseAgent, ABC):
     """
     The primary base class for all implementation agents.