SAFETY-125: a grid charge counts a late meter reading's seconds; the guard row says "over" when it is

A meter reading late near a quarter's end left seconds the projection did
not count (SAFETY-99), and charge_headroom_w() read them as room: the cheap
run (and price trading, and the N=2 maintenance charge) went back to full
power in the quarter's last seconds and the quarter could land over a banked
month peak or the cap. peakguard.charge_room_w() counts those seconds at the
held reading for the charge only; the guard's floor is unchanged.

The guard row said "idle, heading for 5 814 W, under this month's 5 413 W
peak". Over the limit at the current rate the row and the month-peak line
now say so, and that the grid charge is cut back.

Version 0.19.2, CHANGELOG, DECISIONS. test_safety125.py new; the lag pins
in test_price_run_fixes.py and test_opt20.py and the AST pin in
test_arbitrage.py follow the change (see the pull request).

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

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

@@ -0,0 +1,9 @@
+# SAFETY-125 - a grid charge under the month peak
+
+**Status: FIXED in 0.19.2 (hotfix from 0.19.1).** Tests: `test_safety125.py`.
+
+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. Evidence (repro on 0.19.1, sweep, digests): the SAFETY-125
+pull request.