OPT-11 P4 review: records and text

- DECISIONS: the Cheap hours change and why; the no-sun replay (the gain is
  Leftover solar buying the evening's shortfall; the forecast added 0.14
  EUR); the reconstruction bias stated plainly.
- DOCS: Cheap hours ignores the forecast; a reading from before midnight
  is stale.
- The forecast line: "Solar still to come today: ..." (it is what is
  left, and it stays within the 12-word limit).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

goodwe_controller/DECISIONS/OPT-11-battery-modes.md

@@ -94,7 +94,8 @@ P1 is its section 6 P1, and the pull request lists what was measured.
   - Leftover solar may then charge from the grid up to min(ceiling, floor +
     the house's use in the expensive runs / 0.95), less its sun share: only
     the shortfall.
-  - Cheap hours only charges up to the ceiling less its sun share.
+  - Cheap hours only ignores the plan and fills to the ceiling (design
+    section 1; review of #156, see the replay below).
   - Solar first never charges from the grid (owner, 2026-09-29).
 - The level is kept unless it moves by min(1 kWh, 10 %). With no plan
   (no, stale or failed forecast, no house profile, no capacity) every mode
@@ -114,9 +115,15 @@ P1 is its section 6 P1, and the pull request lists what was measured.
   - the days' real 2026 quarter-hourly prices (held out): P2 32.26, option A
     32.01, old trade 31.40, P4 29.19 (perfect 29.21, too high 29.28, missing
     32.01).
-  - Solar first + Cheap hours only: 19.57 on both P3 and P4 (year-earlier
-    prices); on real 2026 prices P4 29.72 against P3's 29.41. Skipping the
-    sun's share does not pay for Cheap hours there; Leftover solar is the
-    mode the forecast pays for.
+  - Solar first + Cheap hours only, skipping its sun share (the first
+    build): 19.57 (same as P3) and 29.72 against P3's 29.41. The shorter,
+    moved runs left B lower, so later midday top-ups rested A while the sun
+    shone. Cheap hours now ignores the plan, which is P3 exactly.
+  - A forecast of no sun at all gives 19.14 and 29.33. So nearly all of the
+    gain is Leftover solar buying the evening's shortfall in the cheap run;
+    the forecast itself was worth 0.14 EUR in 16 September days.
+  - Bias: the site's solar is rebuilt from the same net use the replay
+    plays, and "recorded" keeps its hourly shape and adds only the national
+    daily error. Both favour P4; "national" (no house leakage) gives 29.25.
   No threshold was tuned to these days. The 2026-09-24 PV recording could not
   be replayed: it is only in the live Home Assistant.