Fan/thermal control done and bench-verified; docs updated

BRINGUP records the gate as complete with tach-verified results;
LIGHTBURN.md documents the per-layer Air Assist toggle driving the
cut-profile ventilation; fan_test.py joins the bench kit.

scripts/bench/README.md

@@ -10,6 +10,8 @@ target board (dev image, python3 present) unless noted.
 | `check_pwm.py` | Laser PWM register check (audit M8): reads PWM2 PWMCR/PWMPR via /dev/mem, expects divider 13 × ~127 counts ≈ 40 kHz. |
 | `pwm_sweep.py` | LASER_PWM scope test (runs on the board): `check` = read-only safety readbacks + PWM2 dump; `sweep` = steps PWMSAR through 50/25/75/6/100 % duty with 4 s holds, then restores. Run only in the locked state (controller stopped, cnc disabled, latch locked). Waveform gate PASSED with it 2026-08-02: 40 kHz stable, duty tracks PWMSAR (6.4 % measured vs 6.3 % commanded at the low end). |
 | `pwm_hold.py` | Holds one PWMSAR value for a scope-measurement window (`pwm_hold.py <sar> <seconds>`), then restores. Same locked-state rule. |
+| `fire_test.py` | FIRE drop-timing scope test (runs on the board): A = latch locked (expects nothing on FIRE/LASER_ON), B = latch unlocked / normal end-of-data, U = true underrun. Duty 0 throughout; refuses to unlock if HV reports good. All gates PASSED with it 2026-08-02 (2.0000 s pulses exact, both paths). |
+| `fan_test.py` | Fan/coolant bench (Windows-side): snapshots fan PWMs/tachs/temps, drives M8 → cut fans, M9 → cooldown → idle, verifying via tach readbacks. All-green 2026-08-02. |
 | `build-glowforge.sh` | Cross-compiles **grblHAL-glowforge** (the canonical driver repo, `../../../grblHAL-glowforge`) in the forge-yocto WSL distro. Run: `wsl -d forge-yocto -- bash <path>/build-glowforge.sh` (from PowerShell; Git Bash mangles /mnt/c paths). This is the production controller build. |
 | `build-feeder.sh` | Cross-compiles `feeder.c` the same way. |
 | `puls_profile.py` | Decodes factory `.puls` streams (raw or GF1-headered) into velocity/accel profiles: peak speeds, ramp-slope fits, per-move segments, Z cadence. Runs anywhere (stdlib only). Source of the factory-true grblHAL defaults (milestone 2): 700/590 mm/s² accel, 200 mm/s max rate, 28160 Hz travel tick. |