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/config.yaml

@@ -157,6 +157,11 @@ options:
   # integrations whose sensors fit.
   pv_forecast_entity: ""
   pv_forecast_tomorrow_entity: ""
+  # OPT-17: several forecast sensors per day (one per inverter or string),
+  # summed. Use the list OR the single key above, not both. `[]` is
+  # load-bearing, as for `pv_entities`.
+  pv_forecast_entities: []
+  pv_forecast_tomorrow_entities: []
   solar_trust_pct: 70
 
   # TEL-11 - THE SITE'S PV PRODUCTION, IN WATTS, AND IT IS READ BY NOTHING THAT
@@ -961,6 +966,13 @@ schema:
   battery_modes_enabled: bool
   pv_forecast_entity: str?
   pv_forecast_tomorrow_entity: str?
+  # OPT-17: new list keys beside the single ones. A list schema on the old
+  # keys refuses the string an install stores (tools/supervisor_shape_probe.py
+  # section J); DECISIONS/OPT-17-several-forecast-entities.md.
+  pv_forecast_entities:
+    - str
+  pv_forecast_tomorrow_entities:
+    - str
   solar_trust_pct: int(30,100)
   # TEL-11. Optional, and OPTIONAL WITHOUT A COMPANION RULE - unlike
   # `price_now_entity`/`price_avg_entity`, which are legal only while