SAFETY-125 round 2: the one-inverter maintenance charge is sized to the room too

Owner 2026-10-29: fix N=1 in this hotfix. _charge_headroom() no longer
returns early at one inverter, so the N=1 cheap-window maintenance charge
is held to charge_room_w() as at N=2; SAFETY-84's site-stop rule stays N>=2
only (at N=1 such a stop outranks the shaping anyway). The guard no longer
steps in and gives power at each quarter's end during that charge.

test_safety125.py: N=1 maintenance on 5 s and 10 s meters with late
readings, with and without a banked peak; the row in an N=2 maintenance
charge and in shadow mode; edge cases (blind past the hold, a start
mid-quarter, the summer-time change, the forecast in W, a 10 s meter, the
last second). test_safety84/87: three N=1 pins move. test_safety119: its
quarter-edge hand-back runs keep the old N=1 sizing as a fixture, plus a
check that with the new sizing nothing hands back. CHANGELOG, DECISIONS,
DOCS follow.

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

goodwe_controller/DECISIONS/SAFETY-125-grid-charge-under-the-month-peak.md

@@ -5,6 +5,6 @@
 A grid charge is sized by `peakguard.charge_room_w()`, the guard's headroom
 with the seconds since a late meter reading counted at that reading (the
 projection leaves them out, SAFETY-99, the bill does not), and the guard's own
-floor is unchanged. Not at N=1: the maintenance charge there is not sized to
-the room (SAFETY-84), so SAFETY-99 still applies to it. Evidence (repro on
-0.19.1, sweep, digests): the SAFETY-125 pull request.
+floor is unchanged. At N=1 the maintenance charge is now sized too (owner
+2026-10-29; SAFETY-84 had left it out). Evidence (repro on 0.19.1, sweep,
+digests): the SAFETY-125 pull request.

goodwe_controller/DECISIONS/SAFETY-84-charge-at-two.md

@@ -39,7 +39,8 @@ was fine.
 **Not changed.**
 - At N=1 the charge is not sized to the headroom: the guard still suspends it
   and the battery gives until the quarter is safe. The same sizing would fit
-  there; that is an owner question, not this fix.
+  there; that is an owner question, not this fix. (SAFETY-125, 0.19.2: the
+  owner said yes, and N=1 is sized the same way.)
 - Outside a cheap window (`hi = 0`, solar only) nothing is filed, at any N.
 - A HOLD (later fixed by [[SAFETY-86]]) and the "Battery is not keeping up"
   alarm (SAFETY-85) are untouched. In the identity runs that alarm's log line