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/app/peakguard.py

@@ -1136,6 +1136,21 @@ def charge_headroom_w(decision) -> float | None:
     return max(0.0, -float(decision.wanted_w))
 
 
+def charge_room_w(decision, projection) -> float | None:
+    """SAFETY-125: `charge_headroom_w()` with the seconds since the last
+    meter reading counted at that reading, so a late reading near a
+    quarter's end is not read as room for a grid charge (SAFETY-99).
+    DECISIONS/SAFETY-125-grid-charge-under-the-month-peak.md."""
+    room = charge_headroom_w(decision)
+    if not room or projection is None or projection.block_start is None:
+        return room
+    left = QUARTER_S - float(projection.elapsed_s)
+    if left <= 0.0:
+        return room
+    late_ws = max(0.0, float(projection.held_w)) * uncovered_s(projection)
+    return max(0.0, room - late_ws / left)
+
+
 def shaping_suspended(decision, peak_forecast_w, cap_w) -> bool:
     """Must the maintenance charge-only shaping stand down this cycle?