[FEATURE] Add Debug mode to channel manager

[edenreich]

Summary

When running in debug mode I want to be able to see how many tokens I'm consuming in the current session. This could be a message that is sent along the way in the telegram channel but also ignored when sent back to the LLM.
Similar to how hidden messages are working.
I want to be able to also see when a compact is being triggered in the telegram chat.

Acceptance Criteria

• A debug mode for channel manager is available - could be set either by a command line arg or environment variable
• In debug I can see in the telegram channel how much token the current session contains after each iteration
• The token usage is not sent back to the LLM, it's just for visibility for the user
• It's documented
• It's tested