SAFETY-78: maintenance drain at N=2 no longer stalls

At two inverters the drain pins its pack and the site target is split
around the pin. Below the pin the other pack had to charge, the allocator
refused the opposite directions, and the site sat at 0 W with an ARBITER
line every cycle (house below or above the drain rate, or a grid charge).

main.py now files a site limit `drain` (lo = what the pin places, at
P_MAINTENANCE) at N>=2 while a pack drains, so the other pack only adds
power in the same direction. A drain that cannot give power waits with
one log line. With battery modes on, no grid charge while a pack drains,
and the other battery's card says why. N=1 is byte-identical.

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

goodwe_controller/app/homeview.py

@@ -640,6 +640,11 @@ def battery_rows(c, shadow, running, held=False):
         # carries its share (SAFETY-73)?
         other = next((o.name for o in c.inverters if o is not inv
                       and refusing(c, o) > 0 and not _off(c, o)), None)
+        # SAFETY-78: another battery drains for its monthly cycle, so this
+        # one never charges now.
+        cycling = next((o.name for j, o in enumerate(c.inverters)
+                        if o is not inv and j < len(c.maints)
+                        and c.maints[j].phase == M_DRAIN), None)
         role = None if tick is None else tick.roles.get(inv.name)
         # Only once a cycle has run with modes on (`tick`): before that
         # nothing is known, so nothing is claimed about the prices.
@@ -655,7 +660,8 @@ def battery_rows(c, shadow, running, held=False):
             phase=phase, shadow=shadow, running=running, held=held,
             refused=refusing(c, inv), peak=peak,
             giving=flow(inv.batt) == "giving", other_refuses=other,
-            sf_ahead=sf_ahead, role=role, plan=plan, has_at=bool(at))
+            sf_ahead=sf_ahead, role=role, plan=plan, has_at=bool(at),
+            other_cycle=cycling)
         rows.append({
             "name": inv.name,
             "level_pct": None if inv.soc is None else float(inv.soc),
@@ -673,7 +679,8 @@ def battery_rows(c, shadow, running, held=False):
             # UX-13 P3: why it does what "now" says, from what the add-on
             # knows this cycle. Price and forecast reasons are OPT-11 P3/P4.
             "why_key": why,
-            "why": why_words(why, name=other, at=at),
+            "why": why_words(why, name=cycling if why == "other_cycle"
+                             else other, at=at),
         })
         if modes_on:
             # OPT-11 P1: the battery's switch and mode, for the Batteries
@@ -692,7 +699,7 @@ def battery_rows(c, shadow, running, held=False):
 def battery_why(*, modes_on, mode, off, reading, phase, shadow, running,
                 held, refused, peak, sf_ahead, giving=False,
                 other_refuses=None, role=None, plan=None,
-                has_at=False) -> str:
+                has_at=False, other_cycle=None) -> str:
     """The key of one battery's "why" line (`home_words.why`), most urgent
     first. Pure, so every branch is tested without a controller."""
     if not reading:
@@ -712,6 +719,8 @@ def battery_why(*, modes_on, mode, off, reading, phase, shadow, running,
         return "refuses_give" if refused > 0 else "refuses_charge"
     if peak:
         return "peak"
+    if other_cycle:
+        return "other_cycle"
     if giving and other_refuses:
         return "other_refuses"
     if not modes_on: