Bench: fan_floor_measure.py, the numbers the airflow gates ship with

Two modes. spinup opens a run session with M8 from the engine's idle
posture, samples the four tachometers and the purge-air current once a
second, ends the session with M9 and waits for the engine to leave run;
per fan it reports the steady speed at run duty, the time to 90 percent
of it and the spread over the steady window, the purge current off and
on, and candidate floors at 55 percent of steady. cut sends nothing and
samples while the operator runs a real cut, for the spread the debounce
has to ride over under the only load that matters. Registered on the
bench page as fan-floor. Tooling only; no catalog consequence.

scripts/bench/README.md

@@ -36,6 +36,7 @@ page's takeover does that; from a host, stop them first.
 | `pacing_test.py` | Protocol-loop pacing check (runs on the board, dry motion): idle and parked-in-Hold states are coarse-paced, active motion is tight-paced, and a feed-hold/resume mid-move preserves position with no feeder starve. |
 | `gfbench.py` | Not a tool: the helper the board/host tools share - `HOST`/`LOCAL` from `GF_HOST`, `board(cmd)` (local `sh -c` or ssh), the factory coolant conversion `degc()`, `data_path()` (`FORGETEST_BENCH_DATA` or next to the tool), forgectrl's HTTP API with the panel token, `setting(key)` (from forgectrl, or from `/data/forgefirm.conf` on the board while forgectrl is stopped). |
 | `fan_test.py` | Fan/coolant bench (board or host; controller running): snapshots fan PWMs/tachs/temps, drives M8 → cut fans, M9 → cooldown → idle, verifying via tach readbacks. |
+| `fan_floor_measure.py` | The numbers the airflow gates ship with (board or host): `spinup` opens a run session with M8 from idle and samples the four tachs and the purge current at 1 Hz, reporting per fan the steady speed, the time to 90 percent and the spread over the steady window, plus the purge current off and on, and candidate floors at 55 percent; `cut` samples only, during a real cut, for the spread under load. Results as JSON in the bench data directory. |
 | `flow_characterize.py` | Coolant flow characterization using the factory temperature curve (board or host; forgectrl and controller stopped): baseline → flow → no-flow → recovery, printing the ΔT bands and their separation. Takes the heater duty as an argument (`flow_characterize.py 30`); aborts if downstream passes 45 °C. |
 | `flow_matrix.py` | **The flow-detection design matrix** (board or host; forgectrl and controller stopped; with `flow_sampler.py` from `/usr/share/forgetest/bench/`): duty × duration × flow/no-flow, every run from a common cooled baseline, interleaved repeats. One heating trace yields the metric at every candidate duration, so cost and precision come from the same 60 runs. Prints a cost table, a precision table (mean±sd, worst-case margin, d′) and a ranked shortlist. `flow_matrix.py [duties] [repeats]` (or env `FM_DUTIES`, `FM_REPEATS`, `FM_RESULTS`); results/log in the bench data directory, resumable. |
 | `flow_sustained.py` | Long-run test of the real re-check cadence via M8 (board or host; controller running): counts verdicts/false faults against the configured `cool_flow_rise` and tracks whether the loop accumulates heat. `flow_sustained.py [minutes]`. |