SAFETY-94: a healthy battery that lags or reverses is not flagged as frozen or refusing

The stale-reading gate counted its 35 s from the register's last change, so
after a rest the first read after a new command tripped it (SAFETY-58; live
2026-10-03, four trips 1 s after the command). It now counts only the time
the command asked the register to move.

At N=1 the refusal engaged after 12 frozen cycles if the reading was under
100 W at that moment, which a battery reversing through its lag passes at a
1 s meter. The refusal now needs the N>1 evidence at every roster size: under
100 W, one way, for 12 cycles spanning 22 s, restarting when the reading
moves 50 W towards the ask.

DECISIONS/SAFETY-94-lagging-battery.md; test_safety94.py.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

goodwe_controller/DECISIONS/SAFETY-94-lagging-battery.md

@@ -0,0 +1,94 @@
+# SAFETY-94 - a battery that lags or reverses is not frozen or refusing
+
+**Status: implemented 2026-10-03, for review.** Tests: `test_safety94.py`
+(rig: `tools/safety94_rig.py`). Also closes SAFETY-58. SAFETY-74 stays open.
+
+## The defects
+
+1. **Stale-reading gate (SAFETY-37).** Its 35 s ran from the register's last
+   change. After a rest that clock was already past 35 s, so the first read
+   after a new command tripped it, before the register could answer. Live
+   2026-10-03 (0.14.0, N=2): 17:39:16 B and 17:39:25 A (load ramp after a
+   rest), 19:00:04 A (drain start), 21:21:22 B (drain -> charge). Each was
+   1 s after its command; each register answered within 11 s. This is
+   SAFETY-58's shape.
+2. **Refusal at N=1 (SAFETY-52).** `compute()` engaged after `SETTLE_CYCLES`
+   frozen cycles if the reading was under 100 W at that moment. The frozen
+   cycles include a reversal through the battery's lag. At a 1 s meter the
+   12th cycle comes as a battery reversing out of a charge passes 0 W
+   (SAFETY-85 rig, O1: "gave -20 W for 13 cycles"). The refusal then held
+   0 W, the battery settled at 0 W, never gave 100 W, and waited for the
+   15-minute probe. N>1 already required 22 s in the band, so it was safe
+   at a 10 s lag but not at 20 s.
+
+## What changed
+
+- **The gate counts only time the register was asked to move**
+  (`freshness.Freshness._oblige`). A read counts the time since the last
+  read when, at that read, the command is 250 W or more and has moved 250 W
+  from where it stood at the register's last change. A register change
+  (or a SAFETY-57 release) restarts the count. A command flapping in and
+  out of the ask still adds up (frozen register, 0/1500 W every 5 s: trip
+  at 69 s). The conjunction, `MOVE_W` and `RELEASE_S` are unchanged.
+- **The bound is unchanged at 35 s and now means what its derivation
+  says.** The floor was always "how long a healthy register takes to answer
+  a command": 6 s plant + 10 s publish + 1 s read = 17 s. The band
+  `[2 x 17, 0.5 x 75] = [34, 37.5]` holds. Live answers measured: 1.4, 3,
+  6 and 11 s after the command.
+- **Refusal evidence is the same at every roster size**
+  (`main.Controller._gave_nothing`, SAFETY-73's count moved into a method).
+  The reading must stay under 100 W, one way, while asked over 200 W, for 12
+  cycles spanning 22 s. At N=1 `compute()` gets this as `gave_nothing` and
+  needs it on top of its own freeze test. `None` (compute alone) keeps the
+  old law.
+- **The evidence restarts when the reading moves 50 W towards the ask**
+  (`REFUSED_PROGRESS_W`). A refusing battery reads flat (-3/-4 W live). Live
+  readings wander by under 25 W at rest. A first-order lag crossing the band
+  gains 50 W in at most 0.4 tau, so it cannot fill 22 s unless tau > 54 s.
+  This also covers B, whose reading is 100 W below its power.
+
+## Bounds and worst-case catch
+
+| fault | before | after | budget |
+|---|---|---|---|
+| register frozen, then asked to move | 0-35 s after the ask (often 1 s) | 35 s after the ask (+1 read) | SAFETY-37: 35 s, under the 75/85 s consumer holds |
+| register frozen at rest reading ~0 W | stale 1 s after the ask | refused or stale, 0 W within 23-35 s | the same |
+| refusing battery, 1 s meter, N=1 | 11-16 s | 22-28 s | SAFETY-73's 22 s span (+ one 10 s publish) |
+| refusing battery, 2 s meter | 22-28 s | 22-28 s | unchanged |
+| refusing battery, 5 s meter | N=1 35-41 s, N=2 41-55 s | N=1 40-45 s, N=2 50-55 s | 12 cycles = 55-60 s |
+
+Rig: `test_safety94.py` part 3. A release after SAFETY-57 still exposes
+the held number for one 35 s window of asking, so 35 < 75 < 85 still holds.
+
+## Before -> after
+
+- Live replay (part 1): 4 trips -> 0.
+- Rig, 10 s lag, N=1 and N=2, 1/2/5 s meters, two register shapes, 48 runs
+  (part 2): before 27 stale trips and 1 refusal, after 0 and 0.
+- Reversals, lag 10 and 20 s, 1 s meter (part 2): before N=1 6 stale / 3
+  refused, N=2 6 / 1; after 0 / 0.
+- 16-day loop capture (`test_freshness.py` part 8): 93 trips -> 59. Trips
+  answered within 20 s: 21 -> 1. Two of the removed trips were not quick:
+  a register held 351 s under a command hovering at the 250 W travel edge
+  (under 35 s of asking before it moved; survivor 2's shape), and a
+  refusing battery the gate had caught only on a passing ramp (SAFETY-52's
+  refusal covers it).
+
+## SAFETY-58 and SAFETY-74
+
+- **SAFETY-58 is fixed** by this change: its card asks for the clock to
+  start with the obligation and for the bound to be re-derived. Both are
+  done above. `test_freshness.py` survivor 5 is now graded as closed.
+- **SAFETY-74 is not fixed.** A battery capped at 300 W with a perfectly
+  flat reading, 5 s meter, house stepping: 50 trips/h at N=1 and 80 at N=2
+  before, 37 and 60 after. With +-1 W dither: 0. A flat reading under a
+  command that moved is exactly what the gate is for; telling "limited"
+  from "frozen" needs a second signal (the meter, or SoC).
+
+## Known gaps
+
+- B's standby offset (-95 to -118 W at idle) puts a refusing B outside the
+  100 W band some of the time, so a refusing B may not latch. Pre-existing,
+  not touched here.
+- A register frozen under a command that stays near the 250 W travel edge
+  is caught late or not at all (survivor 2).