OPT-17: the solar forecast can come from several entities, summed

New list options pv_forecast_entities and pv_forecast_tomorrow_entities
(same shape as pv_entities); the single-entity keys are unchanged.

- Each member is read in its own unit (Wh/kWh/MWh) in one gather and the
  day is summed. Hourly splits are merged when every member has one, else
  the total goes on the bell.
- A member missing, unavailable, stale, non-energy or bad makes that
  day's forecast unusable (no partial sum). A caution row names it by
  position; the action log names the entity once per change.
- Single key and list both set for one day: refused at start.
- A one-member list behaves exactly like the single key (test_opt17.py);
  the single-key path is byte-identical to e36565f over 24 scenarios.
- Supervisor shape measured: tools/supervisor_shape_probe.py section J.

DECISIONS/OPT-17-several-forecast-entities.md has the rules.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Bdqr7PiaHcBnzPituu2yTC

goodwe_controller/app/uilayout.py

@@ -135,6 +135,10 @@ GROUPS = (
             Field("pv_forecast_entity", ENTITY, kind="energy", simple=True,
                   note="forecast"),
             Field("pv_forecast_tomorrow_entity", ENTITY, kind="energy"),
+            # OPT-17: several forecast sensors per day, summed.
+            Field("pv_forecast_entities", ENTITY_LIST, kind="energy"),
+            Field("pv_forecast_tomorrow_entities", ENTITY_LIST,
+                  kind="energy"),
             Field("solar_trust_pct", SLIDER, "%", step=5),
         )),
     )),