SAFETY-81 review: 10 s hold, ERROR line per episode, more scenarios

- The alarm must hold for peakguard.ALARM_HOLD_S (10 s) on the projection's
  clock. A load that tops cap + battery for ~5 s every 30 s alarmed at every
  quarter start while the quarter landed under the aim (sine4500_fast).
- A cycle with no battery reading leaves the hold alone.
- Notified once per quarter, but the ERROR line is written per episode.
- New sim scenarios (sine4500_fast, twice7000, step6500_gap) with 5a4cdc2
  digests; control still byte-identical. Unit checks for export and the
  hold across a missing reading. test_peakguard's saturated fixture moves
  the hold start back instead of waiting it out.
- DECISIONS and DOCS updated: costs of the hold, tolerance reasoning, the
  double count in control left to a follow-up.

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

goodwe_controller/DOCS.md

@@ -3212,9 +3212,10 @@ reason code `OUTPUT_CLAMP`.
 **Load too high for battery.** The capacity-peak guard (SAFETY-07) asks for
 everything the inverter can discharge and the running 15-minute average is
 still projected over the peak limit, so the month's billed peak
-(capaciteitstarief) goes up. It fires only when, with the battery at full
-power, the period will still end more than 10 W over the real limit (not the
-margin's aim), and at most once per period (SAFETY-81). In shadow mode the
+(capaciteitstarief) goes up. It fires only when, for 10 s, the period would
+still end more than 10 W over the real limit (not the margin's aim) with the
+battery at full power. It notifies at most once per period; later overloads
+in the same period go to the log (SAFETY-81). In shadow mode the
 guard's projection is made on a plant that did not respond (SAFETY-47), and
 the text says so. See *The capacity-peak guard*.