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/app/arbiter.py

@@ -635,7 +635,7 @@ def site_resolve(claims: list) -> Resolution:
 
 
 def resolve(claims: list, *, units=None, weights=None, live=None,
-            tick=None) -> Resolution:
+            tick=None, reserve=()) -> Resolution:
     """The three stages, in order, over one cycle's claims.
 
     `units` is the site's roster of inverters. Left None it is derived from the
@@ -737,6 +737,13 @@ def resolve(claims: list, *, units=None, weights=None, live=None,
     gate, held = _unit_modes(out, site_claims, bounds, live)
     if callable(weights):
         weights = weights(out.target_w)
+    # SAFETY-87: units under their peak reserve weigh 0 while the site gives,
+    # so the others carry the peak floor. An Off battery gives the peak's
+    # shortfall, so it goes before them when no other unit is left.
+    reserve = set(reserve) if out.target_w > 0.0 else set()
+    if held and reserve and not set(bounds) - held - reserve:
+        held = set()
+    held = held | reserve
     if held:
         weights = {u: (0.0 if u in held else
                        (1.0 if weights is None else weights.get(u, 1.0)))