nx_robot_timing_gate.nx

nx_robot_timing_gate.nx -- R-ROBO-7 GATE: step-timing / timer-ISR rung with never-brick max-rate. VERIFIES: (1) ACCEL profile: schedule starts slow (iv[0] big) and settles to the cruise floor (iv[n-1]==min); (2) overall acceleration: an early interval is clearly larger than a later one; (3) step count preserved; (4) NEVER-BRICK max-rate: EVERY interval >= min_iv (instantaneous rate <= 1/min_iv); (5) EXHAUSTIVE never-brick: sweep accel aggressiveness (incl. absurd) -> min interval always >= min_iv; (6) TIMER-ISR monotonic: steps_fired_by rises with time, 0 at t=0, n at end; (7) NEGATIVE CONTROL: the RAW (unfloored) interval at high index is < min_iv -> the floor (the never-brick rate cap) is doing real work. 100% sovereign, integer-only, hardware-rung-up. license_tier: ORIGINAL expect_exit: 0