Implement Duration Tracking in SwarmAdapter

[aviralgarg05]

Description

Currently ScenarioRun duration is hardcoded to 0.0 in src/agentunit/adapters/swarm_adapter.py.
The adapter already calculates duration_seconds for metrics (line 374), this should be converted to ms and used in ScenarioRun.

Source

https://github.com/aviralgarg05/agentunit/blob/main/src/agentunit/adapters/swarm_adapter.py#L345

Task

• Update SwarmAdapter.end_session to correctly populate duration_ms in ScenarioRun.