Add delegation tracking for multi-agent orchestration

[evansenter]

Background

The Opus 4.5 training analysis document mentions explicit training on:

• "Hierarchical task decomposition trajectories"
• "Subagent coordination patterns"
• "Explicit supervision on delegation decisions"

Currently agent-event-bus tracks sessions and broadcasts, but doesn't capture the structure of task delegation.

Proposal

Add tools for tracking delegation relationships:

delegate_task

{
  "parent_session_id": "abc123",
  "child_session_id": "def456",
  "task": "Review PR #42 for security issues",
  "context": "Parent is working on feature branch, needs security review",
  "expected_output": "List of security concerns or approval"
}

complete_delegation

{
  "delegation_id": "del_xyz",
  "status": "completed",
  "result": "No security issues found. Approved.",
  "tokens_used": 1234
}

get_delegation_tree

Returns the hierarchy of task delegations for a root session.

Value

1. Visibility: See how work is being decomposed
2. Training data: Export delegation patterns for fine-tuning
3. Debugging: Trace failures through delegation chains
4. Metrics: Track delegation efficiency (tokens, success rate)

Implementation Notes

• New delegations table tracking parent→child relationships
• Could integrate with session lifecycle (auto-complete on session end)
• CLI: agent-event-bus-cli delegations --tree <session_id>