Hooks: Provide the name of the agent when there is a SubagentStop event.

Question

**Bug Description**
```js
{
   "cwd" : "/home/user/src/claude-hooks",
   "hook_event_name" : "SubagentStop",
   "permission_mode" : "default",
   "session_id" : "0a9258bd-acdd-47db-91ef-34a4c73b695e",
   "stop_hook_active" : false,
   "transcript_path" : "/home/ewheeler/.claude/projects/-home-ewheeler-src-claude-hooks/0a9258bd-acdd-47db-91ef-34a4c73b695e.jsonl"
}
```

Provide the name of the agent when there is a SubagentStop.

**Environment Info**
- Platform: linux
- Terminal: vte-based
- Vers