Persona:
- Fix [STATUS: completed|limit_reached] reference (format was removed)
- Clarify three fields: task / briefing / system_prompt with distinct roles
- Clarify context_transfer vs briefing: transfer = working state, briefing = credentials

Secretary system_prompt:
- Replace vague "write all context to context_transfer" with explicit field breakdown
- task / briefing / system_prompt each described with their purpose
- context_transfer correctly limited to intermediate findings, not credentials

Server admin system_prompt:
- Same fix: explicit field breakdown for spawn_agent
- Remove dangling "see persona" reference for briefing ending

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