Preserve LightSwarm runtime context

[helloJamest]

Summary

Closes #79.

This PR preserves LightAgent runtime context across LightSwarm entry runs and delegated handoffs.

Changes:

• allow LightSwarm.run(..., **run_kwargs) to forward supported LightAgent.run() options;
• pass runtime context such as user_id, metadata, trace, result_format, max_retry, and max_tool_iterations to delegated target agents;
• keep existing handoff trace hierarchy via parent_trace_id and run_group_id;
• add regression tests for the entry-agent path and the delegated handoff path.

This does not automatically merge delegated traces into the source agent trace. It only preserves the existing explicit context and trace hierarchy knobs across the LightSwarm path.

Tests

python -m pytest