v0.8.0 - cli compact + pinned session

cli /compact now works: closes the window, summarizes the live session, restarts the window on the compacted session. Runner auto-detects a cli agent live session (newest jsonl). The active session_id is pinned in the agent topic and stored in fleet.agents (pin_msg_id, migration 003) so both owner and agent know it; pin updates on session change.