docs: fix SubagentStart inconsistency in hook-events.md

[philoserf]

Problem

In hook-events.md, SubagentStart is referenced in the "Agent-Level vs Settings-Level Hooks" comparison section:

Agent-level hooks can respond to agent lifecycle events like AgentStart and SubagentStart

However, SubagentStart does not appear in the main hook events table earlier in the document. This creates confusion about whether it's a valid event.

Solution

Either:

Option A (if SubagentStart exists): Add it to the main events table:

| SubagentStart | Fires when a subagent is spawned | agent_id, parent_agent_id, agent_type |

Option B (if SubagentStart doesn't exist): Remove the reference from the comparison section:

Agent-level hooks can respond to agent lifecycle events like AgentStart...

Recommendation: Verify against Claude Code's actual hook events and choose the appropriate option.

Files to Update

• references/hook-events.md

Impact

• Priority: High
• Effort: Low
• User Impact: Fixes documentation inconsistency that could cause user errors

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Review context: commit f2fe29b (agent hooks documentation)