SAFETY-87 review: maintenance pins beside a held battery

A draining battery that may still give is raised from its drain rate
towards its rating for the peak floor while another battery is held
(peak > drain); before, the floor's rest landed on the held battery. In a
HOLD, a held battery's own pin counts among the others: a held drain no
longer over-places the site, and a held charge probe no longer parks it.

Tests: test_safety87.py part 10 (drain beside a held battery, N=3 HOLD,
unknown cut-out and unread level at N=3, a stopping row outranks the
running peak alarm). DECISIONS entry updated, incl. the modes-on exception.

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

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

@@ -45,7 +45,15 @@ graded on its own floor, and an unread SoC or unknown cut-out counts as held.
 The min/max pairing still decides permission, over the able batteries. The
 roster verdict `decide()` echoes (`soc`, `soc_floor`) is kept, so SAFETY-32's
 call-site and reduction checks still bite. What changed is only that one held
-battery no longer stops the others.
+battery no longer stops the others. One exception, with battery modes on: see
+Open.
+
+**Maintenance pins beside a held battery** (review). A draining battery that
+may still give is raised from its drain rate towards its rating for the peak
+floor, after the others (`_drain_over_reserve()`; peak > drain), else the
+floor's rest landed on the held battery. In a HOLD, a held battery counts its
+own pin (a drain) among the others, and a held battery pinned to charge stops
+the raise (never split both ways).
 
 **Before -> after** (test_safety87.py, rig of 2 x 2500 W, aim 3450 W):
 
@@ -66,7 +74,9 @@ battery no longer stops the others.
   says "cannot keep … alone", not "will go over", so it stays true.
 - Battery modes on, A Off and B held: when B alone can place the floor, OPT-11
   keeps A resting and B gives it. When B cannot, A gives first. Making Off give
-  before a held battery in the first case needs a third allocator tier.
+  before a held battery in the first case needs a third allocator tier. The
+  same at N=3: A Off, B held, C able, floor 4000 W gives C 2500, B 1500, A 0.
+  Until then, with modes on, a held battery can give for the peak.
 - The notification and row text live in `messages.py`, which has no NL layer
   yet (UX-19). The Home page text, which has NL, is unchanged.