OPT-34: the night charge keeps its level when the kept forecast ends

With the forecast sensors silent from 17:05 the kept evening figure ended at
midnight + 3 h, in the middle of the night grid charge, and Leftover solar's
planned level went with it (rig: A 49.8 % against 79.9 %).

- A night grid charge that has started keeps its planned level when the forecast
  goes (Controller._latch_charge, store key night_charge_latch), and the narrow
  price gap with it (weather_held). A fresh figure still moves the level.
- The evening's tomorrow figure is today's until the bell starts (06:00 local),
  up to 15 h old but only if it was usable at midnight (solarfc.Hold.stand_in).
- Screen: "No solar forecast now. The charge under way goes on to its planned
  level." (EN/NL) while a latched battery is below its level.
- test_opt34.py (whole nights through the real control cycle, mutants), test_opt27
  and test_modes_p4 adjusted to the new window and the kept level.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Bdqr7PiaHcBnzPituu2yTC

goodwe_controller/DECISIONS/OPT-27-last-fresh-forecast-for-the-night.md

@@ -19,14 +19,16 @@ still keeps a run under way when a read is lost.
 **The rule** (`Hold.stand_in()`). A kept reading is for one day. It covers a
 sensor that is missing or stale, never one with a bad value or unit, and:
 - for up to `FRESH_S` when the sensor is missing: a short outage, any time of day;
-- from the end of the bell (20:00 local, `BELL_TO_H`) until local midnight + 3 h
-  (`KEPT_UNTIL_H`), if the reading is at most `KEPT_MAX_AGE_S` (12 h) old when used;
+- from the end of the bell (20:00 local, `BELL_TO_H`) until local midnight, if the
+  reading is at most `KEPT_MAX_AGE_S` (12 h) old when used; after midnight the
+  tomorrow figure is today's until the bell starts (06:00), up to 15 h old
+  (OPT-34 changed this from midnight + 3 h);
 - the day it is for: a today figure only on that day, a tomorrow figure as
   tomorrow until midnight and, if the today sensors are still stale, as today's
-  until midnight + 3 h (all sensors of the sum are needed, as for any sum);
+  until 06:00 (all sensors of the sum are needed, as for any sum);
 - until the next fresh reading, which replaces it at once.
 
-So a figure is never used for another day and never older than 12 hours (`KEPT_MAX_AGE_S`): a 17:05 reading serves until 03:00 (9 h 55 min), a 09:05 reading only until 21:05.
+So a figure is never used for another day and never older than 12 hours (`KEPT_MAX_AGE_S`), except the morning case above: a 17:05 reading serves until 06:00 (12 h 55 min), a 09:05 reading only until 21:05. Until OPT-34 the figure ended at 03:00, and a charge under way lost its level there; OPT-34 closes that limit.
 Daytime is as before: a sensor that stopped is stale after 3 h, and no forecast
 all day is still no forecast (the night run still needs 1.5x).
 

goodwe_controller/DECISIONS/OPT-34-the-night-charge-keeps-its-level.md

@@ -0,0 +1,53 @@
+# OPT-34 - the night charge keeps its level when the kept forecast ends
+
+**Status: done on `release/1.0`, not released.** Tests: `test_opt34.py`.
+
+**The defect** (OPT-27 rig test, F-1). The kept evening figure ended at midnight + 3 h.
+With the sensors silent from 17:05 the Leftover solar battery's level went with
+it in the middle of the charge: A ended at 49.8 % against 79.9 % with a fresh
+figure. Whether Forecast.Solar refreshes after midnight on a live site is not
+known, so the add-on does not depend on it.
+
+**The rule.**
+1. *A charge under way keeps its level* (`Controller._latch_charge()`). While
+   there is a forecast (fresh or kept), each battery that charges from the grid in the
+   cheap run takes its planned level into a latch (store key `night_charge_latch`).
+   With no forecast, `plan_targets()` gives the latched level, and the wide
+   no-forecast gap does not refuse the next slice of the run (`weather_held()`,
+   as TARIFF-24 does for the run under way). While a
+   forecast is there the latch follows the plan, up or down as a fresh figure moves
+   it. It lasts through every cheap run on and one price slot after the last.
+2. *The evening's tomorrow figure is today's until the bell starts*, 06:00 local
+   (`BELL_FROM_H`, `solarfc._bell_start()`), not until midnight + 3 h.
+   Nothing has been produced yet, so it is still the whole day.
+3. *Up to 15 h old for that case only* (`KEPT_MORNING_MAX_AGE_S`): a 17:05
+   reading is 12 h 55 min old at 06:00. It must have been at most 12 h old at
+   midnight, so a 09:05 reading, unusable since 21:05, does not come back for five
+   minutes after midnight. Same-day figures and the daytime rule keep 12 h and 3 h.
+4. A fresh figure replaces the kept one at once, as before.
+
+**Step 1 alone is enough for the owner's shape, steps 2-3 are still needed.**
+With the window put back to midnight + 3 h the owner's night still ends as a
+fresh figure ends it (A 86.9 %, B 95.0 %), because the charge had started at
+22:00. But a charge that has not started by 03:00 (the price dips at 04:00, or
+the headroom is taken) has no level to latch: A ends at 38 % against 78 %. The
+plan, the screens and a restart also need the figure itself.
+
+**Screens.** "Solar forecast read {at}, kept for tonight." is still true until
+06:00 and unchanged. After the figure ends, with a charge still going on: "No
+solar forecast now. The charge under way goes on to its planned level." /
+"Nu geen zonneprognose. De lopende lading gaat door tot het geplande niveau."
+(`home_words.solar.latched`, only while a latched battery is below its level).
+
+**Not used.** A figure over 15 h old; a morning figure at night (12 h); a figure
+for another day; a bad value or unit; and no latch for a charge that has not
+started, for a battery that is not charging, or after the cheap runs have ended
+(plus one slot).
+
+**Not changed.** Charge sizing, the peak guard, Cheap hours, modes off, arbitrage.
+A fresh figure that LOWERS the level during a charge still lowers it, as before.
+
+**Mutants** (all red in `test_opt34.py`): no latch; window back to midnight + 3 h;
+15 h without a limit; no "usable at midnight" rule; the latch without the narrow
+gap, without its save, or not kept through the next run; the window 6 h after
+midnight instead of 06:00 local (DST); 15 h cut to 12 h; the new screen line off.