Firstmate adds token-efficient daemon mode

Agentic workflows are notorious for burning tokens on idle polling loops. Gating supervisor escalations behind an explicit `/afk` command is a brilliant, resource-conscious pattern that more frameworks should adopt.

• –**Presence-Gated Scaling**: Using `/afk` lets developers transition from high-responsiveness mode to background supervision dynamically without changing their core configuration.
• –**In-Band Sentinel Marker**: The implementation uses a hidden unit separator marker (`FM_INJECT_MARK`) in the terminal stream to prevent autonomous output from cancelling the AFK state.
• –**Robust Terminal Integration**: The update introduces crucial injection safeguards like supervisor pane auto-discovery, busy guards, and turn-confirmation retries to handle unstable TUI/tmux layouts.
• –**Massive Cost Reductions**: Moving routine heartbeats to a local bash watcher results in a 65–75% reduction in LLM API token consumption for unattended runs.