laser power-good: the line characterized, the kernel-drill guard, the probe, the dev image's mmap and ctypes

The supply's power-good line is active high, static across HV enable and emission, and driven; the facts bank and CAMPAIGN-LOG carry the measurement and the item closes. The kernel-drill latch-unlock guard read the old inverted value as HV not good, a check that was vacuous and would refuse every run once the module reads the line correctly; it now uses the chain's own witnesses, the charge-pump watchdog and the engine state. pgood_probe.py watches the line beside the chain through the kernel readbacks and is registered on the bench page. The dev image lists python3-mmap and python3-ctypes again for the pad-level bench tools the python trim had left without them.

scripts/bench/README.md

@@ -59,6 +59,7 @@ page's takeover does that; from a host, stop them first.
 | `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: 700/590 mm/s² accel, 200 mm/s max rate, 28160 Hz travel tick. |
 | `cp_watchdog_timing.py` | HV charge-pump watchdog one-shot timing (runs on the board): latches every CHG_PUMP feed pulse in GPIO3's edge detector (pin 24 only, IMR untouched, ICR2 restored on exit) and polls the `!Q` (`charge_pump_alive`) and `!HV_ENABLE` (`hv_enable`) pads through /dev/mem in a tight loop while it commands short local jogs; prints per-run t_w (last pulse → Q fall), Q → HV_ENABLE delay, priming latency and the feed period, with the loop's worst gap as the resolution. Motion only, laser locked, no other Grbl client attached. |
 | `resume_dark_lead.py` | Pause/resume safety-chain timing (runs on the board, as root): samples LASER_ON, FIRE, HV_ENABLE, the charge-pump watchdog, the button and the doors straight off the SoC pads through /dev/mem at ~2 kHz, with motion dated from the kernel step counters, across a pause and a resume driven by the operator's button presses. Reports how long HV_ENABLE survives the stream stopping, how fast the chain re-arms on the resume, and - on `--run live` - the dark lead between FIRE going back on and LASER_ON following it, in milliseconds and in millimeters at the job's feed. `--run dry` (default) commands no laser at all and `--auto P,R` drives the pause and resume with `!`/`~` for an unattended rehearsal; `--run live` needs the arm press, eye protection, fire watch, extinguisher and exhaust. GRBL mode, no other Grbl client attached. |
+| `pgood_probe.py` | The supply's power-good line (J1_14, `cnc/laser_pgood`) against the laser chain, without a scope (runs on the board, as root): polls the kernel readbacks (`laser_pgood` reported as the raw pin level, `laser_on`, `laser_enable`, `charge_pump_alive`) and the switch device's HV_ENABLE and doors bits at a few hundred hertz, `hv_current` at 20 Hz, and prints every transition with a timestamp plus a per-line summary. Drive the machine meanwhile (a dry jog, an armed cut, a pause, a lid open); the probe only watches. Feed it over ssh stdin: `ssh root@<board> 'python3 - --secs 90' < pgood_probe.py`. |
 | `bench_m2.py` | Motion-quality bench, runs against the board over TCP:23: bounded round-trip jogs (sanity, max-rate, diagonal) + feed-hold/resume mid-move, reporting peak feed, state transitions, and position drift. |
 
 Data files kept beside the tools: `flow_matrix_results.json` /