TARIFF-02: one canonical price format, and a seam that keeps supplier names out of the optimiser

Five provider plugins - generic_dayahead, engie_dynamic,
totalenergies_dynamic, eneco_eddy, manual_csv - all emitting exactly
{"prices": [{"start", "eur_per_kwh", "provisional"}]}, tz-aware at the
Brussels offset, EUR/kWh, all-in. Nothing consumes it yet; the seam
lands first, per the PM's ordering.

It is built in goodwe_controller/app/ rather than at specs.md 2.2's
ems/ingest/prices/, per the product owner's decision of 2026-08-30. The
behaviour 9.3 / 8.3 / 11.4 specifies is unchanged.

Three things shape the design, and each is the mechanism rather than a
comment saying to be careful:

Double-counting the markup is unreachable. A plugin does not return a
price - it returns the figure its source published and declares which of
{energy, markup, taxes} that figure already contains. assemble() adds
the complement, once, in the framework. A plugin is never handed
price_markup_eur_kwh: PluginOptions raises FrameworkOption on it, so the
line that adds the margin a second time cannot be written. Engie and
TotalEnergies publish a retail figure with their margin inside; adding
the configured 3 c/kWh on top would have made every arbitrage decision
wrong by that amount with nothing reporting it.

The product type is declared, not inferred from the plugin's name.
eneco_eddy is real-time/imbalance and gets 8.3's widened thresholds
through capabilities().product and volatility_regime(), never through a
name comparison - which is AC2. test_price.py asserts mechanically that
no plugin id appears anywhere in the framework's code, and drives a
sixth provider defined inside the test file to the right regime with
price.py untouched.

"No price data" is a type, not an empty list - the same rework
sim/riglock.py took under TEST-04. A fetch returns PriceRead.series(...)
or PriceRead.no_data(reason), and only the first carries fields. An
empty series is not constructible; no_data has no .points, no .at(), and
.get("points", []) raises rather than returning the default. A day of
free electricity and a day with no prices are different instructions -
arbitrage is pointless under one and forbidden under the other - and an
implementation returning [] cannot tell them apart. Every site-level
failure returns no_data; nothing raises into the control tick.

Also: injection stays a separate scalar (export_price_eur_kwh, AC4),
negative prices survive the boundary validator (17's regression case),
egress is allow-listed against each plugin's own declaration (16), and
no tzdata is used - the shipped Alpine image has none, so Brussels
offsets come from the EU rule and instants are carried as UTC.

validate.py grows rule 7: an unknown provider id, manual_csv with no
path, and - the HA overlap the PM told us to decide about -
price_provider set alongside price_now_entity/price_avg_entity, which is
two price sources where the HA pair silently wins. The HA sensors are
kept and still work alone; TARIFF-03 and OPT-04 are what replace them.

CFG-03 is not widened: the price defaults have ONE in-code mirror,
PRICE_OPTION_DEFAULTS, which validate.py imports rather than restating
and which test_price.py pins to config.yaml by reading the file.

test_price.py is runnable, assert-free in the house style, and every
verdict it prints is derived. It grades the markup arithmetic with
0.031/0.057 rather than the shipped 0.03/0.06, because 0.06 is exactly
twice 0.03 and a degenerate pair would make double-counting
indistinguishable from correct addition - and it asserts that
non-degeneracy as its first section. The DST checks run on the 23-hour
and 25-hour days, not on a normal day where a fixed 24-slot
implementation and a correct one agree. Thirteen mutations were driven
through it; all thirteen go red.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015VXjA3LWccN1rJsk3okyPC

goodwe_controller/CHANGELOG.md

@@ -2,6 +2,63 @@
 
 ## Unreleased
 
+**Price provider plugins, and one canonical all-in price format (TARIFF-02).**
+`app/price.py` ships five providers - `generic_dayahead` (wholesale EPEX BE),
+`engie_dynamic`, `totalenergies_dynamic`, `eneco_eddy` and the offline
+`manual_csv` - all emitting exactly `{"prices": [{"start", "eur_per_kwh",
+"provisional"}]}`, tz-aware at the Brussels offset, EUR/kWh, all-in. **Nothing
+consumes it yet**: this is the seam, landed first, so that the arbitrage work
+that follows never learns a supplier's name.
+
+**Double-counting the markup is unreachable rather than discouraged.** A plugin
+does not return a price; it returns the figure its source published and
+declares which of {energy, markup, taxes} that figure contains. The framework
+adds the complement, once. A plugin is never handed `price_markup_eur_kwh` at
+all - `PluginOptions` raises on it - so the plugin that adds the margin a second
+time cannot be written. Engie and TotalEnergies publish a retail figure with
+their margin already inside; adding the configured 3 c/kWh on top would have
+made every future arbitrage decision wrong by that amount with nothing
+reporting it.
+
+**The product type is declared, not inferred from the plugin's name.**
+`eneco_eddy` is a real-time/imbalance product and gets widened arbitrage
+thresholds; that reaches a consumer through `capabilities().product` and
+`volatility_regime()`, never through a name comparison. `test_price.py` asserts
+mechanically that no plugin id appears anywhere in the framework's own code,
+and drives a sixth provider defined inside the test file to the correct regime
+with `price.py` untouched.
+
+**"No price data" is a type, not an empty list.** Following the same rework
+`sim/riglock.py` took, a fetch returns `PriceRead.series(...)` or
+`PriceRead.no_data(reason)`, and only the first carries fields. An empty series
+is not constructible; `no_data` has no `.points` to iterate, no `.at()`, and
+`.get("points", [])` raises rather than returning the default. **A day of free
+electricity and a day with no prices are different instructions** - arbitrage is
+pointless under the first and forbidden under the second - and an implementation
+that returns `[]` on a failed fetch cannot tell them apart. Every site-level
+failure returns `no_data`; nothing raises into the control tick.
+
+**`manual_csv` is the documented offline fallback** and needs no network, no
+supplier account and no HTTP stack. See DOCS.md for the format. Its `start`
+column must carry a UTC offset - a bare local timestamp is refused, because one
+hour every October names two moments.
+
+**Injection is priced separately** (`export_price_eur_kwh`), a scalar rather
+than a second series, and negative values are accepted. Consumption plugins
+cannot reach it.
+
+**`price_provider` may not be combined with `price_now_entity` /
+`price_avg_entity`** - the add-on refuses to start on that pair. The Home
+Assistant sensors are the existing delegation of pricing to HA and still work
+alone; with both configured they would silently keep deciding while the status
+page named a supplier that decided nothing.
+
+**No timezone database is used.** The shipped Alpine image has no `tzdata`, so
+Brussels offsets are computed from the EU rule and every instant is carried as
+UTC and rendered at the offset that applies to it. The checks drive both 2026
+transitions - the 23-hour and 25-hour days - rather than a normal day, where a
+fixed 24-slot implementation and a correct one agree.
+
 **A computed setpoint over the rating now alarms instead of being clipped in
 silence (SAFETY-03).** The clamp was never the missing half - specs.md 10.3
 records an unclamped integrator climbing ~130 W per 4 s past 10 kW and reporting