forgetest: the lid lamp idles at forgectrl's lid_lamp_idle; the liveness test masks and restarts

The lid lamp now has a resting policy in forgectrl (lid_lamp_idle,
default 236, asserted at start and at every spawn), so the baseline
expects it there instead of preserving whatever level a boot left, and
forgectrl.settings-bounds proves it: resting at the setting, 256 / -1 /
'bright' refused, a new level applied to the lamp at once, the cleared
key back to the default. Clearing a key goes through the query-string
form (an empty JSON value reads as no setting).

motion.liveness-probe adds the regression the bench needed: with every
axis masked (cnc/motor_lock=15, as a bench tool may leave it) forgectrl
is restarted and its fresh probe must read MOTION OK on the first try -
the probe unmasks the axes itself - and the controller comes up with the
mask cleared. Bench 2026-08-16: MOTION OK at p2p 2047/1341 against the
800 threshold, no ladder.

The baseline's settle no longer counts 'probe verified, spawn pending' as
settled (the post pass ran between the probe's own writes and the
controller's init writes and mis-flagged motor_lock/step_freq): it waits
for the controller to be running, with a bounded allowance for a respawn
backoff.

docs/ACCEPTANCE.md

@@ -112,11 +112,12 @@ items: **fixed** resting values the boot establishes (the kernel module
 defaults, forgectrl's start-up writes, the GRBL controller's init writes:
 `motor_lock=8`, `x/y_mode=8`, `x/y_decay=1`, `step_freq=28160`,
 `ramp_rate=125000`, `streaming=0`, `state=idle`, latch locked, hold
-currents, camera lamps and button LEDs off, heater and TEC off; forgectrl:
-the controller running with motion verified, no diagnostic, the camera
-engine and cooling engine idle), and **preserved** state with no resting
-policy that a run must hand back as it found it (the lid lamp level, the
-position counters, the settings map, the controller mode). Deviations are
+currents, head lamp and button LEDs off, heater and TEC off, the lid lamp
+at forgectrl's `lid_lamp_idle` setting; forgectrl: the controller running
+with motion verified, no diagnostic, the camera engine and cooling engine
+idle), and **preserved** state with no resting policy that a run must
+hand back as it found it (the position counters, the settings map, the
+controller mode). Deviations are
 **leftovers**: logged in the run pane, kept in the result's `evidence`
 (`baseline.pre` / `baseline.post`), and surfaced in the page's message
 line - a leftover found before a run is attributed to the previous run; one
@@ -129,12 +130,11 @@ verified, or the ladder's verdict) before and after every takeover.
 **Power-cycle before a campaign.** forgetest takes a **fresh-boot
 reference** once per boot (`/data/forgetest/boot-<boot_id>.json`, taken
 only within the first ten minutes after boot, after the supervisor
-settles): the whole idle picture of this machine as the image boots it. It
-is the session's resting lid-lamp level and the check on the fixed values;
-without one the lamp level is unknown and the page says so. Take it after
-a **power cycle**, not a warm `reboot`: the PIC lights the lid lamp at
-power-on (132), and a warm reboot leaves it dark because the module's
-remove path turns it off - the machine's true fresh state is the lit one.
+settles): the whole idle picture of this machine as the image boots it,
+the check on the fixed values, and the record a leftover is judged
+against. Take it after a **power cycle**, not a warm `reboot` - the
+machine's true fresh state is the powered-on one (the PIC's own lamp and
+sensor defaults, then forgectrl's start-up writes on top).
 A displaced head is jogged back along its own path by the kernel-measured
 X/Y delta (bounded to 100 mm; Z is never touched); beyond that the
 counters are reported and the run must be fixed. A run that legitimately