SAFETY-126 round 2: state what the 10 W tolerance costs; test the latch reset

Text only (DECISIONS, DOCS, CHANGELOG): a step load alarms on the same cycle
as before; a steadily rising load alarms a little later; with peak_margin_w 0
a period can end up to 10 W over the limit without this alarm, as for 'Load
too high' (SAFETY-81). Owner accepted 2026-10-31.

test_safety126.py part 2: after a real overrun ends, _peak_landing()'s latch
is reset and the night's later landings are quiet (review F3).

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

goodwe_controller/DOCS.md

@@ -3458,7 +3458,7 @@ Charging from the grid stays blocked meanwhile. With several inverters the
 notification names the battery at its limit (SAFETY-32), each graded against
 its own cut-out level. That battery is held (weight 0 while the site gives)
 and the guard's need goes to the others, up to their rating; the alarm fires
-only if they miss the limit at full power for `ALARM_HOLD_S` (SAFETY-87). With no battery able to give it fires at once, but only if the period would end more than 10 W over the aim with the batteries at 0 W. A grid charge the add-on runs counts as one it can stop, and the last second's landing error on the aim is not an alarm (SAFETY-126). ⚠️ **The reserve binds the peak guard only
+only if they miss the limit at full power for `ALARM_HOLD_S` (SAFETY-87). With no battery able to give it fires at once, but only if the period would end more than 10 W over the aim with the batteries at 0 W. A grid charge the add-on runs counts as one it can stop, and the last second's landing error on the aim is not an alarm. A steadily rising load therefore alarms a little later. With `peak_margin_w` 0 a period can end up to 10 W over the limit without this alarm, as for “Load too high” (SAFETY-126). ⚠️ **The reserve binds the peak guard only
 (SAFETY-25).** Self-consumption has no such floor. See *What `peak_soc_floor`
 does not protect*.