FCST-04: the carry-forward fill reaches the plan, and the day it carries survives a restart

FCST-03 shipped `fill_from_yesterday()` complete and checked, and shipped the
consumers written for it - `TariffPlan.firm_points()`, `cheap_now()`'s refusal
of a provisional hour, and `arbitrage()`'s refusal 3, which drops provisional
hours from the trade set rather than refusing the whole series. It shipped NO
CALLER. Nothing in `app/` named the fill, so no series ever contained a carried
point and every one of those consumers was exercising its all-firm branch.

⚠️ THE DEFECT THAT PRODUCED WAS NOT AN ERROR ANYWHERE. `load_prices()` returns
what the feed published and nothing widened it to the requested horizon, so on
a dynamic site between midnight and the 14-16 h CET publication the plan
covered the rest of today and nothing more - measured on the fixture here, 24 h
against a 48 h request. `arbitrage()` then took `max - min` over that truncated
window and reported a spread. The number was real, the window was half the one
configured, and nothing said so: tomorrow evening's peak, the hour a morning
charge would be sold into, was not in the series to be compared against
anything. A missing hour is not a wrong price - it is an hour the optimiser
never learns exists.

WHAT THIS ADDS. `app/price_history.py` keeps the PUBLISHED prices of the last
KEEP_DAYS Brussels days in /data/price_history.json; `resolve_tariff()` gains a
required keyword-only `history` and fills every unpublished hour of the horizon
from yesterday's same-wall-clock hour, flagged. Persistence rather than a
variable on the refresh task, because the window the fill exists for is
midnight -> publication and an add-on restarted at 08:00 would otherwise spend
all of it on the truncated series. Not in state.json: the refresh runs every
1800 s and that file holds the maintenance history and SAFETY-02's latch.

⚠️ ONE CHANGE HERE MOVES ENERGY, AND IT IS NOT THE ONE THE CARD IS NAMED FOR.
Carried hours are provisional, so §8.3 keeps them out of the trade set: the
fill widens what the optimiser can SEE, never what it may DO, and
test_price_history.py checks that so it cannot be overclaimed later. What does
change a trade is that the filled series is windowed to [since, until), so
hours that have ALREADY ELAPSED are no longer in the spread. Before, a cheap
night that had gone sat in the series as the day's cheapest hour - and a cycle
cannot buy in an hour that is past, so the trade was quietly never taken.
Section 2 grades this by finding the cheapest firm hour with and without the
fill and showing it MOVES, from 02:00 UTC to 08:00 UTC on the fixture.

⚠️ A DEAD FEED IS STILL §11.4, NOT YESTERDAY. The fill runs only on a `series`
read. The two are indistinguishable to the optimiser - both 100 % provisional,
so arbitrage refuses on the firm-pair rung and `cheap_now()` is False - so
preferring yesterday's feed over the `static_profile` an operator configured
FOR that case would change a documented degradation for a difference only the
status page can see. That, and two more, in
DECISIONS/FCST-04-the-day-that-is-carried.md.

⚠️ THE ANTI-DECAY RULE IS AN ORDERING, NOT A VALIDATION, and saying so is more
useful than a guarantee that would not hold. Feeding the filled series back in
is how this rots - day 2 carries day 1's guesses, day 3 carries day 2's carry
of them, behind a `provisional` flag that stays TRUE while the NUMBER decays.
No value-level check can catch it: a carried point and `eneco_eddy`'s
published-provisional quarter are the same three fields with the same flag. So
`carry()` is the only public entry, it records BEFORE it fills, the filled
series exists only as a return value the object never sees again, and
test_price_history.py walks app/ for any other module naming `_remember` and
reads `carry()`'s AST to pin the order.

EVIDENCE. 29/29 test files pass in the CI image. Eight mutations driven against
app/price_history.py and app/static_tariff.py, __pycache__ purged before each
run per MUTATION.md/TEST-15: newest-record lookup (5 red), recording the filled
series (1), replace-instead-of-merge (10), UTC-date keying (10), removing the
fill call entirely (12), a lost price field defaulting to 0.0 (2), prune by
clock arithmetic (1), a degraded reason that stops naming its cause (1). No
survivors; baseline and revert both green. Three of those first crashed the
harness instead of reporting a FAIL - "it was refused" and "it broke on the way
to being refused" must not grade the same - so `why()` and `_priced()` were
added and the run repeated.

No option added, config.yaml untouched, and the CHANGELOG entry deliberately
picks no version: PKG-07's rule, and only the deployer knows whether 0.9.0's
image has been pulled.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BwRLw7eKYj2byVdwB6kbjU

goodwe_controller/CHANGELOG.md

@@ -1,5 +1,75 @@
 # Changelog
 
+## Unreleased
+
+⚠️ **THIS HAS NO VERSION AND CANNOT REACH AN INSTALL UNTIL IT GETS ONE.**
+PKG-06's and PKG-07's rule: the Supervisor keys the built image by `version:`,
+so `ha apps update` is a silent no-op on an unbumped change. This branch
+deliberately does **not** pick the number, because the right one depends on a
+fact the branch cannot observe - whether 0.9.0's image has already been built
+and pulled. If it has not, this belongs inside 0.9.0's section before it ships;
+if it has, it needs 0.10.0. Whoever deploys decides.
+
+| | |
+|---|---|
+| _this branch_ | FCST-04 - the carry-forward fill reaches the plan, and the day it carries survives a restart |
+
+**FCST-03 shipped the fill and no caller.** `price_forecast.fill_from_yesterday()`
+was complete and checked, and so were the consumers written for it -
+`TariffPlan.firm_points()`, `cheap_now()`'s refusal of a provisional hour, and
+`arbitrage()`'s refusal 3, which drops provisional hours from the trade set
+rather than refusing the whole series. Nothing in `app/` called the fill, so no
+series ever contained a carried point and every one of those consumers was
+exercising its all-firm branch.
+
+⚠️ **THE DEFECT THAT PRODUCED WAS NOT AN ERROR ANYWHERE.** `load_prices()`
+returns what the feed published and nothing widened it to the requested horizon,
+so on a dynamic site between midnight and the 14-16 h CET day-ahead publication
+the plan covered the rest of today and **nothing more** - typically 10-24 of the
+48 hours `price_horizon_h` asked for. `arbitrage()` then took `max - min` over
+that truncated window and reported a spread. The number was real, the window was
+half the one configured, and **nothing said so**: tomorrow evening's peak, the
+hour a morning charge would be sold into, was not in the series at all, so the
+spread it would have created was never compared against anything.
+
+**What changes:**
+
+* `app/price_history.py` (new) keeps the **published** prices of the last
+  `KEEP_DAYS` Brussels days in `/data/price_history.json`, and
+  `resolve_tariff()` now fills every unpublished hour of the horizon from
+  yesterday's same-wall-clock hour, flagged provisional.
+* `resolve_tariff(history=...)` is **required and keyword-only**. A caller with
+  no durable volume passes the explicit `NoHistory()`. A default of `None`
+  meaning "skip the fill" would hand a caller who forgot the argument exactly
+  the truncated horizon this card removes, silently.
+* A new status row, **Price history**, names the days held and their hour
+  counts.
+
+⚠️ **ONE CHANGE HERE MOVES ENERGY, AND IT IS NOT THE ONE THE CARD IS NAMED FOR.**
+Carried hours are provisional, so §8.3 keeps them out of the trade set: the fill
+widens what the optimiser can **see**, never what it may **do**. What does
+change a trade is that the filled series is windowed to `[since, until)`, so
+**hours that have already elapsed are no longer in the spread**. Before, a cheap
+night that had already gone sat in the series as the day's cheapest hour - and a
+cycle cannot buy in an hour that is past, so the trade was quietly never taken.
+`test_price_history.py` section 2 grades this by finding the cheapest firm hour
+with and without the fill and showing it **moves**.
+
+⚠️ **A DEAD FEED IS STILL §11.4, NOT YESTERDAY.** The fill runs only on a
+`series` read; a feed that published nothing still degrades to the configured
+`static_profile`. The two are indistinguishable to the optimiser - both are
+100 % provisional, so arbitrage refuses on the firm-pair rung and `cheap_now()`
+is False - so preferring yesterday would change a documented degradation for a
+difference only the status page can see.
+`DECISIONS/FCST-04-the-day-that-is-carried.md` carries that and two more.
+
+⚠️ **A BROKEN CACHE IS NOT A BROKEN CONTROLLER.** No `/data`, an unreadable
+file, a schema this build does not know, a malformed point - four states, four
+reasons, none of them a price and none of them an empty series. In every one the
+plan is still a real provider series and the controller still regulates; the
+horizon is just as short as it was before this card. **No option was added and
+`config.yaml` is untouched.**
+
 ## 0.9.0
 
 ⚠️ **MINOR FOR NEW FUNCTIONALITY, NOT FOR A BREAK - AND THAT DISTINCTION IS THE