fix: use rtc_mw as fallback for client_load when ppa_capacity is not set

- Fallback order: client_load_mw -> ppa_capacity_mw -> rtc_mw

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

packages/engine/src/remodel_engine/scenarios/runner.py

@@ -483,10 +483,14 @@ def run_scenario(inputs: ScenarioInput) -> ScenarioResult:
     from datetime import datetime, timedelta
 
     cod_year = inputs.project.cod_year
-    # Default client load to ppa_capacity if not set
+    # Default client load: use client_load_mw if set, else ppa_capacity, else rtc_mw
     client_load_mw = inputs.commercial.client_load_mw
     if client_load_mw is None:
         client_load_mw = inputs.commercial.ppa_capacity_mw
+    if client_load_mw is None or client_load_mw == 0:
+        # Fallback to rtc_mw if available
+        if inputs.rtc is not None and inputs.rtc.rtc_mw > 0:
+            client_load_mw = inputs.rtc.rtc_mw
 
     # Transmission + aux loss factor for client_end
     loss_factor = 1.0 - inputs.commercial.aux_consumption_pct - inputs.commercial.transmission_loss_pct - inputs.commercial.dsm_loss_pct