Monitoring and Tracing via Log Streams (per-agent)

Generate an event log to consume in observability platforms like Axiom/DataDog, to generate dashboards, alerts, etc.

We can emit structured JSON events for the status of the requests. These can happen with the default log level, or opt-in by setting logLevel in the Agent initializer to TRACE or EVENTS or something.

Might also be useful when using an agent as a tool to have per-tool reports with all the tools used

emit per-step (per-message?):

agent name
threadId
userId
whether it's a tool
model
status