e24bac49fa
In HUD mode Hermes is a strip over the app the user is actually working in, so "what's under you?" or "look up the weather" is almost always about that app — but the agent had no way to know it was floating, and answered from its own browser and panes instead. The desktop tags a HUD submit with `surface: 'hud'` and the gateway turns that into a per-turn note pointing at read_window_below, and at carrying the work out in the app underneath. It rides the model-bound message beside the reaction and speech-interrupted notes rather than the system prompt: one session can be driven from the app window on one turn and the HUD on the next, and the system prompt has to stay byte-stable. Every tool the note names is checked against the agent's own schema first, so a session without computer_use or read_window_below is never pointed at a tool it cannot call.