SAFETY-87: peak guard uses every battery that can still give

At N>=2 a battery at or under its own peak reserve is held: it gives
nothing for the peak (weight 0 while the site gives) and the guard's need
is placed on the live, non-refusing batteries above theirs. The guard is
floor-limited, and alarms, only when those cannot hold the limit at full
power for ALARM_HOLD_S. The peak alarms no longer read "Not ready" or hold
the Home page at 0 W, because control keeps running. N=1 is byte-identical.

DECISIONS/SAFETY-87-guard-uses-able-batteries.md.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019DBUfvndgHwaV339Fvd2gr

goodwe_controller/test_safety86.py

@@ -337,7 +337,8 @@ HOLDING = [MaintResult(HOLD, True, 0.0, False, []),
 def pin_after(floor, *extra, live=(A, B), results=HOLDING, c=_c):
     fake = types.SimpleNamespace(inverters=c.inverters,
                                  actuator_of=c.actuator_of,
-                                 live_units=lambda: tuple(live))
+                                 live_units=lambda: tuple(live),
+                                 _peak_reserve=frozenset)
     cl = [Claim.limit("supervised", P_SAFETY, -2500.0, 2500.0, actuator=A),
           Claim.limit("supervised", P_SAFETY, -2500.0, 2500.0, actuator=B),
           Claim.set("maintenance", P_MAINTENANCE, 0.0, HOLD, actuator=A),