OPT-11 P3: price runs per battery

Cheap and expensive hours as runs of consecutive firm price slots
(priceruns.py); each battery's role per tick from its mode (modetrade.py):
grid charging for Leftover solar / Cheap hours only, never Solar first;
holding for the expensive runs; selling per battery (pack_sell) above the
spread and the floor. The site trade is sized inside the modes (loop bound)
and the peak guard's headroom; a run edge reseeds the loop. Cheap hours only
and selling are enabled on the Batteries screen and in the HA select
(appended). The site Why row no longer says "held back" when the peak limit
pushes power up (F2). Modes off: byte-identical to 7a00f12 on the trade path.

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

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

@@ -29,4 +29,34 @@ P1 is its section 6 P1, and the pull request lists what was measured.
   page's English names, pinned by a test, and are not renamed with the page:
   automations send them.
 - In P1 only Off closes a direction; Leftover solar differs by charging last.
-  Price runs, selling (`pack_sell`, reserved) and the forecast are P3/P4.
+- P3 (price runs, `priceruns.py`, `modetrade.py`): each battery's range is
+  narrowed by its role this tick (hold, give, charge, rest, sell); main.py
+  files the intersection with the switch, so it still holds 0 W. With modes on
+  the site trade is filed by the modes, sized from the loop bound (so no
+  battery a mode or a refusal holds is asked for watts, P1's unmet share) and
+  the guard's headroom; `arbitrage.decide()` runs only with modes off, which
+  stays byte-identical to 7a00f12 (`test_modes_p3.py` part 1).
+- SAFETY-46 item 2 is decided as the owner answered (2026-09-25): a trade is
+  a run of consecutive firm slots. It applies with battery modes on; the
+  modes-off trade keeps its one-period shape, because that path must not move.
+- Choices that were measured, not assumed (tools/opt11p3_replay.py):
+  - a sale needs the guard to have measured the quarter, not to be clear: a
+    5 kW discharge alone reads "engaged" on export and flipped the sale every
+    5 s;
+  - a grid charge makes the others rest, so it starts only at 500 W and, once
+    the guard or the headroom stops it, stays off for that 15-minute period
+    (without: 13 flips in 4 minutes under a 3.5 kW house);
+  - stored energy is valued at the last cheap run for 12 h, and a charge
+    needs its own run to clear the spread (without: a night charge was spent
+    on flat morning prices, then charging went on at them);
+  - a run edge reseeds the loop at the house's level (a 3 kW import spike
+    removed; about 0.1 x rating still overshoots as export).
+- Replay (tools/opt11p3_replay.py, 16 recorded days, EPEX prices a year
+  earlier, modelled batteries): P3 does not beat the P2 baseline on money
+  (net 19.57 / 19.60 EUR against 19.33; the old one-period trade 18.14).
+  A sale is judged on import prices but exports earn the injection price,
+  so selling lost money in the model. The owner should see this before
+  selling is recommended.
+- Not done in P3: the forecast (P4: Leftover solar acts as Cheap hours only),
+  a headroom too short for the run moving the rest to the next cheap periods,
+  and an HA switch for selling.