bench: every board-runnable tool ported to the bench page

The remaining bench diagnostics run from forgetest's #bench tab. The
tools that also run from a LAN host share scripts/bench/gfbench.py:
GF_HOST names a remote machine (host mode, sysfs through ssh, Grbl and
forgectrl over the LAN); unset, the tool runs on the board itself
(local mode, sysfs directly, everything on 127.0.0.1), which is how the
page runs them - with GF_HOST=127.0.0.1, the panel token in GF_TOKEN
and their data files under <data>/bench/ (FORGETEST_BENCH_DATA). The
helper also reads a machine setting from forgectrl, or from the settings
file on the board while forgectrl is stopped.

Ported: pwm_sweep / pwm_hold (scope = a takeover; the latch relocked,
the write refused if FIRE or LASER_ON reads active), pwm_stream_test
(PASS/FAIL exit), flow_characterize, flow_recheck_char,
flow_warm_validate and flow_matrix (takeovers: forgectrl owns the
thermal hardware, so the page's takeover replaces the tools' own
controller stop/restart, whose command line predated the supervisor;
results and logs in the bench data directory), flow_sustained,
fan_test, temp_calibrate (dry; watch bounded in seconds; the threshold
and the coolant conversion from the shared code), flow_escalate_drill
(cool_confirm_max_s shortened through forgectrl's settings for the
drill and restored; the setting's minimum is the default budget), and
live_fire_drills (<drill> [S] [F], all six drills, host from GF_HOST,
token from the board). flow_matrix joins the registry. What stays
unported cannot run against the machine at all: the two null-sink CI
harnesses and the .puls decoder.

Runner: a scope tool runs inside the takeover wrapper; the bench
environment above is passed to every tool. Tests: test_bench_registry
(registry <-> scripts/bench consistency, every ported tool builds its
command line, every script compiles, gfbench host/local modes) and the
server test (scope tool takeover, the environment reaching the tool).
Local mode smoke-run on the bench (temp_calibrate watch, setting, token)
from /tmp, removed after.

No catalog consequence: bench tools are not image components (dev-only
forgetest); the acceptance catalog is unchanged.

scripts/bench/fan_test.py

@@ -1,18 +1,18 @@
-import shlex, socket, subprocess, time
-import os
+#!/usr/bin/env python3
+"""Fan/coolant bench: snapshots the fan PWMs, tachs and coolant readings,
+drives M8 (cut-profile fans), then M9 (cooldown -> idle), and prints
+each snapshot for the tach readbacks to be judged. Needs the controller
+running with forgectrl's cooling engine. Runs on the board or from a
+host (gfbench: GF_HOST)."""
+import socket
+import time
+
+from gfbench import HOST, board as _board, degc
 
-HOST = os.environ.get('GF_HOST')
-if not HOST:
-    raise SystemExit('set GF_HOST to the machine IP address')
-# ssh client used to reach the board; override for a wrapper, e.g.
-# GF_SSH='wsl -d <distro> -- ssh'.
-SSH = shlex.split(os.environ.get('GF_SSH', 'ssh'))
 
 def board(cmd):
-    r = subprocess.run(SSH + ['-o', 'PreferredAuthentications=none',
-                              'root@' + HOST, cmd],
-                       capture_output=True, text=True, timeout=30)
-    return r.stdout.strip().replace('\n', ' ')
+    return _board(cmd).strip().replace('\n', ' ')
+
 
 ATTRS = ('head/air_assist_pwm head/air_assist_tach head/purge_air '
          'thermal/exhaust_pwm thermal/tach_exhaust '
@@ -44,7 +44,7 @@ time.sleep(0.5); drain()
 
 snap('--- baseline (driver idle profile)')
 w2 = board('cat /sys/glowforge/pic/water_temp_2')
-print('water_temp_2 = %s -> %.1f C' % (w2, int(w2) * -0.09653 + 94))
+print('water_temp_2 = %s -> %.1f C' % (w2, degc(w2)))
 
 print()
 print('=== M8: cut-profile fans ON (loud) ===')