SAFETY-126: a landing error on the aim is not an overrun

During the night grid charge under the peak reserve the guard alarmed
(ERROR PEAK_GUARD_FLOOR_LIMITED, "Battery stopped limiting the peak") and the
Batteries "Why" said "The peak limit needs power" at quarter ends, while every
quarter landed on the aim. The charge lands the period 0-7 W over the aim and
excess_w()'s 900 / remaining turns that into tens of kW in the last second;
with nothing able to give, check_peak_floor_limited() alarmed on any
wanted > 0.

Each cycle the guard wants power, _peak_landing() asks misses_aim(): with the
batteries at 0 W, does the period end more than ALARM_MISS_W over the aim? If
not, the decision is within_aim: no reserve alarm, no red peak row, no "Why"
peak. The claim and the commands are unchanged. A real overrun under the
reserve alarms on the same cycle as before.

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). ⚠️ **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 (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*.