- ToolResult.output now prefixed with explicit reminder that the user
  cannot see sub-agent output and the orchestrator must present findings
  in its own final response; reminder appears adjacent to the result so
  the model reads it in context
- spawn_agent description updated: lowers threshold from "3+" to "2+"
  tool calls, makes USER CANNOT SEE warning prominent, tightens wording
- persona.txt DELEGATION section: clearer rule (default to spawning for
  multi-step sub-tasks), explicit "never end turn after spawn results",
  removed abstract threshold in favour of concrete examples

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>