agent semantics

iocane models systems in terms of agents, not just microservices. an agent is any autonomous execution unit that makes decisions, spawns work, calls tools, or retries actions.

• identity: derived from span attributes (agent.id, agent.name).
• roles: agents are classified as planners, workers, or tool executors based on behavior.
• traffic classes: distinguishes between tool calls, token streams, and checkpointing operations.