nx_ferment_thermal.nx

nx_ferment_thermal.nx -- R1 hardware rung: vessel temperature hold. Composes nx_pid (control loop) + nx_ferment_safety (the never-poison envelope CLAMPS every commanded setpoint, so the loop can NEVER target a temperature above culture-kill). Heat-only actuator model (a yogurt/cheese vessel heats; cooling is passive loss to ambient) -- the cheapest real hardware. TWO independent safety layers, so no PID mistuning can cook a culture: 1. setpoint CLAMP at construction (kill - margin), and 2. a hard thermal INTERLOCK in every step: at/above the ceiling the heater command is forced to 0 regardless of the controller. With a bounded per-step heat (heater_max * heat_gain) smaller than the margin, the vessel can never cross culture-kill in a single step. Proven by the gate: unsafe setpoints clamp; the command is heat-only and bounded; a room-temperature vessel is driven up into the setpoint neighborhood; and temperature NEVER reaches culture-kill across the whole run (the ceiling holds DYNAMICALLY, not just at config time). genealogy_id: ziegler_nichols_1942_pid (via nx_pid) + nishi_ferment_safety_envelope_2026 (via nx_ferment_safety)