MAINT-24: keep the refusal probe beside a maintenance charge

The mode trade still lets a SAFETY-73 probe (PROBE_W alone) go on while a pack
is in its maintenance CHARGE phase; test_opt20.py g7 pins it. ch_ch_maint
digest moved (B no longer grid-charges beside A's charge).

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

goodwe_controller/app/modetrade.py

@@ -199,7 +199,8 @@ def decide(runs, now, packs, *, charge_ok, sell_ok, trade_why, price_now,
     charge from the grid (why "cycle"). `wait` ("wait" or "settle", the
     why) says no charge may start yet (SAFETY-135). `maint_charging` says a
     battery is in its maintenance CHARGE phase: no grid charge for the others
-    either, same why (MAINT-24, DECISIONS/MAINT-24-charge-first.md).
+    either, same why, but a refusal probe goes on (MAINT-24,
+    DECISIONS/MAINT-24-charge-first.md).
     """
     plan_on = runs is not None and runs.on
     in_cheap = plan_on and runs.cheap.holds(now) and runs.charge_useful()
@@ -209,8 +210,12 @@ def decide(runs, now, packs, *, charge_ok, sell_ok, trade_why, price_now,
     why = None
     ch = chargers(packs, ceiling_pct, done_charge, targets, probe=True) \
         if in_cheap else []
-    if ch and (draining or maint_charging):
+    if ch and draining:
         ch, why = [], "cycle"
+    elif ch and maint_charging:
+        # MAINT-24: a refusal probe (PROBE_W alone, OPT-20) may go on.
+        ch = [p for p in ch if p.refused < 0]
+        why = None if ch else "cycle"
     charging = False
     if ch:
         need = 0.0 if charging_now else START_W