PRICE-02 round 2: require now, undo the test loosening, analyse ties

- TariffPlan.arbitrage(now=...) is required (keyword-only, no default); so are
  homeview.trade_verdict/refusal_key's now. Existing test calls pass one.
- test_arbitrage.py: no module-level decide wrapper. Fixtures that probed a
  one-day plan after its extremes now hold two days (as a site does); the
  flap day gets a unique cheapest and dearest hour; the replay breaks its
  ties without direction. The flap bound is <= 4 and the replay check is
  len(_trades) < 365 again. 228 checks pass on the old and the new code.
- test_price02.py part 6: ties (equal quarters, a real 15-minute day,
  alternating hourly prices) and the required now.
- Identity pins: the masked digest is only for the older-tree comparison;
  this tree's own digests are pinned with nothing hidden.
- DECISIONS: the tie analysis with numbers.

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

goodwe_controller/DECISIONS/PRICE-02-the-verdict-skips-ended-periods.md

@@ -17,7 +17,9 @@ ended (`end <= now`, the span `price._cover_table()` gives, as
   still used at 03:20, and the Home chart keeps the day's earlier bars.
 - An hourly point that is still current stays in, so hourly feeds and the
   static day/night plan give the same verdict as before.
-- `now=None` keeps the old reach (the whole series); only tests leave it out.
+- `now` is required: keyword-only, no default, like the other three arguments. A
+  caller that could leave it out would get the elapsed periods back and the
+  defect with them. A test that wants the whole series passes an instant before it.
 - The sentences of this verdict in `arbitrage.py` (status row and action log,
   English only) say "price period" where they said "hour": the idle one now
   reads "now is not the cheapest or the dearest price period". The UI texts
@@ -30,3 +32,38 @@ the same too; only a sale's sentence quotes a smaller "above the cheapest"
 figure once the first cheap period is over. The identity pins in
 `test_modes_p3.py` and `test_price_run_fixes.py` hide just that figure and the
 word change (`opt11p3_identity.trade_digest()`).
+
+## Ties (round 2)
+
+The verdict takes `min`/`max` over the points still ahead and the first one wins
+a tie, so with equal prices it is the first period still ahead, which is the
+current one. Before, it was the first of the whole plan, often one that had
+ended. Two effects follow, and both are the card's intent, not a side effect:
+
+- Equal quarters (hour-constant data, or a feed that prints the same price in
+  several quarters) now act in every quarter of the cheap (or dear) block,
+  not in the first only. Test: `test_price02.py` part 6.
+- After the cheapest period has passed, the next cheapest still ahead is the
+  target, if its spread still clears the cost. A hourly plan did this at every
+  refresh already (it started at the current hour); a 15-minute plan did it
+  only from the next hour on, because it kept the elapsed quarters of this one.
+
+Measured with `scratch/PRICE-02/dev/tiesim.py` (refresh every 30 min from the
+floored hour, verdict at 7 min into each period, threshold 0.05, old = the
+verdict over the whole plan, new = this card):
+
+| data | days | acting periods old -> new | action changes old -> new |
+|---|---|---|---|
+| real 15-minute day, energy-charts 2026-09-09 | 1 | 4 -> 5 | 6 -> 6 |
+| real 15-minute days 2026-09-09 and -10 | 2 | 14 -> 26 | 24 -> 24 |
+| EPEX 2025-26 hourly prices as four equal quarters | 12 | 18 -> 72 | 36 -> 20 |
+| the same with random +-0.002 noise per quarter (no ties) | 12 | 18 -> 33 | 36 -> 48 |
+
+So a real 15-minute day does not switch more often (24 -> 24), and a day of
+equal quarters switches less. A synthetic day of noisy, tie-free quarters does
+(3.0 -> 4.0 changes a day): each period that passes hands the target to the
+next cheapest one ahead. Every change is still at a period edge, never within
+one. The replay in `test_arbitrage.py` (synthetic year, hourly) gives the same
+ledger on the old and the new code once its ties are broken (280 round trips,
+85 held, both): it printed one maximum twice per day, and the old fixture
+tested the first of them only because its plan began at midnight.