TARIFF-03: static day/night and fully-fixed tariffs, first-class

§9.2 puts a large share of the Belgian installed base on a static profile, and
an EMS that only works under dynamic pricing is an EMS for a minority. A new
`static_profile` option describes a two-period day/night tariff - or a single
fixed price - and app/static_tariff.py turns it into the same canonical
{start, eur_per_kwh, provisional} series the fetched providers emit.

Not a sixth provider plugin, for two mechanical reasons. capabilities() is a
classmethod, so a plugin's PriceProduct is fixed when the class is written -
but §9.2 makes STATIC and FIXED two different products and which one a site is
on is a property of the operator's data; StaticProfile.product derives it from
the number of distinct prices. And the plugin framework exists to stop a
FETCHED figure being marked up twice, which a number typed as all-in cannot be.
So the profile sits where §11.4 already says it does - under the providers, as
the fallback. Configured product and feed-is-down are one generator differing
in one flag, so the degradation path cannot rot unused.

"No arbitrage" is a type. TariffPlan.arbitrage() returns a variant whose
ALLOWED arm carries the spread and the cheapest/dearest hours and whose REFUSED
arm carries a reason and nothing else - .spread_eur_kwh on a refusal raises
rather than answering 0.0, so an optimiser cannot compute a trade from one.
Four refusals, all derived: peak guard holding, no price data, plan
provisional, or the series is FLAT. The last is AC2: a fixed tariff disables
arbitrage by arithmetic, not by matching on an enum. peak_guard_active is a
required keyword argument, so §10.1's priority 2 over 3 cannot be skipped.

Time-window shifting reaches the one shiftable load that exists: main.py's
cheap-window flag falls back to the static profile, and the UI gained a Tariff
row. Cheap is STRICTLY below the seven-day mean - `<=` would call every hour of
a flat tariff cheap, and 48 h taken on a Friday is two-thirds weekend.

A profile must tile every day type exactly once, checked at startup; a gap is
refused with the range named rather than filled in. `22:00-07:00 mon-fri` does
not cover Saturday morning, and that trap is what the check catches.

validate.py rule 7's stated reason expired exactly as TARIFF-02 predicted: the
test_price.py section 12 tripwire went red naming static_tariff.py. The message
now says what is true instead, and the tripwire is re-aimed rather than removed
- consumer set pinned, expired phrase asserted gone. Rule 7 also grew a second
refusal for static_profile alongside the HA price pair, the same silent-loser
conflict and a live one.

CFG-03 is not widened: static_profile went into price.py's PRICE_OPTION_DEFAULTS
- the one in-code mirror pinned to config.yaml by a check - and the new module
carries no defaults dict of its own.

Measured on the two committed days of this house's real P1 meter. 2026-08-20
(Thursday): 15.220 kWh imported, 9.606 day / 5.614 night, EUR 4.7185 under
day/night vs EUR 4.6725 flat, shifting saves EUR 0.8069 = 9.606 kWh x the
0.0840 spread, derived twice. 2026-08-23 (Sunday): 0.728 kWh, all of it
night-priced, which is the weekend row proving itself. §17 names six Belgian
scenarios; this is the seventh, and it is two days rather than a season - the
file says so rather than implying an annual figure.

All 12 suites green. Eleven mutations of static_tariff.py were each caught by
at least one check.

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

goodwe_controller/config.yaml

@@ -204,6 +204,37 @@ options:
   price_horizon_h: 48
   price_timeout_s: 10
 
+  # --- static / fully-fixed tariffs (TARIFF-03, specs §9.2 / §11.4) ----------
+  # §14's `tariffs.static_profile`, and "" is its `null`. §9.2: "a large share
+  # of the installed base is on [a static profile]" - this is what makes those
+  # sites first-class rather than "price_provider: off, good luck".
+  #
+  # A JSON object, on one line, whose periods must tile every day type exactly
+  # once - no gap and no overlap. A gap is REFUSED at startup rather than
+  # defaulted, because an invented price is one an optimiser would trade on.
+  # A fully-fixed tariff is ONE period covering 00:00-24:00, all days; the
+  # add-on derives "fixed" from there being one distinct price, so there is no
+  # box to tick and none to tick wrongly.
+  #
+  #   {"periods": [
+  #      {"name":"day",  "from":"07:00","to":"22:00","days":"mon-fri","eur_per_kwh":0.34},
+  #      {"name":"night","from":"22:00","to":"07:00","days":"mon-fri","eur_per_kwh":0.26},
+  #      {"name":"night","from":"00:00","to":"24:00","days":"sat,sun", "eur_per_kwh":0.26}]}
+  #
+  # ⚠️ A window written "22:00-07:00 mon-fri" does NOT cover Saturday morning -
+  # a period applies on the day the CLOCK reads, so the weekend row above is
+  # required, not decorative. See DOCS.md.
+  #
+  # eur_per_kwh is ALL-IN (energy + markup + taxes, §9.3), the same basis the
+  # dynamic providers are assembled onto. price_markup_eur_kwh and
+  # price_taxes_eur_kwh are NOT added to it.
+  #
+  # ⚠️ RECOMMENDED EVEN ON A DYNAMIC SITE. §11.4's degradation row is "no price
+  # data -> fall back to the static profile"; with this empty there is nothing
+  # to fall back to and a dead feed leaves the site with no tariff at all.
+  # validate.py warns about exactly that.
+  static_profile: ""
+
   # §9.3: injection is priced SEPARATELY, and in Belgium it is often near zero -
   # which by itself strongly favours self-consumption over export. A scalar, not
   # a second series: no shipped supplier publishes a dynamic injection curve.
@@ -296,6 +327,11 @@ schema:
   price_feed_url: str?
   price_horizon_h: int(1,72)
   price_timeout_s: int(2,60)
+  # A JSON string rather than a nested schema, deliberately: it is ONE option
+  # key (§14 has one), it survives config.yaml's flat options block, and
+  # parse_static_profile() accepts an already-parsed dict too, so a future
+  # nested schema is a config.yaml change and no code change at all.
+  static_profile: str?
   # ⚠️ The lower bound is NEGATIVE on purpose. Belgian injection tariffs have
   # gone below zero (you pay to export at midday in summer), and a schema that
   # bottoms out at 0 would make that site inexpressible.