fix: correct hourly index calculation for 25-year data

- Reset index per year caused out-of-bounds error
- Simplified loop using sequential hour_idx 0-8759 per year

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

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

@@ -508,26 +508,37 @@ def run_scenario(inputs: ScenarioInput) -> ScenarioResult:
         fy_start = cod_year + year
         fy_label = f"{fy_start}-{str(fy_start + 1)[-2:]}"
 
-        # Generate timestamps for this year
-        hour_idx = 0
-        for month in range(12):
-            month_len = month_lengths[month]
-            for day in range(1, month_len + 1):
-                for hour in range(24):
-                    # ISO timestamp
-                    month_num = month + 4 if month < 8 else month - 8
-                    year_adj = fy_start + 1 if month >= 8 else fy_start
-                    dt = f"{year_adj:04d}-{month_num:02d}-{day:02d}T{hour:02d}:00:00"
-                    hourly_timestamps.append(dt)
-                    hourly_fy.append(fy_label)
-                    hourly_proj_year.append(proj_year)
+        # Run through each hour sequentially (0 to 8759)
+        for hour_idx in range(8760):
+            # Map hour_idx to month/day/hour
+            hour_of_year = hour_idx
+            # Find month by cumulative hours
+            cum_hours = 0
+            for m in range(12):
+                month_len = month_lengths[m]
+                if hour_of_year < cum_hours + month_len * 24:
+                    month = m
+                    day_of_month = (hour_of_year - cum_hours) // 24 + 1
+                    hour_of_day = (hour_of_year - cum_hours) % 24
+                    break
+                cum_hours += month_len * 24
 
-                    idx = year * 8760 + hour_idx
-                    total_re = pipe.solar_hourly[idx] + pipe.wind_hourly[idx]
-                    hourly_total_re.append(total_re)
-                    hourly_client_end.append(total_re * loss_factor)
-                    hourly_load.append(client_load_mw)
-                    hour_idx += 1
+            # ISO timestamp
+            month_num = month + 4 if month < 8 else month - 8
+            year_adj = fy_start + 1 if month >= 8 else fy_start
+            dt = f"{year_adj:04d}-{month_num:02d}-{day_of_month:02d}T{hour_of_day:02d}:00:00"
+            hourly_timestamps.append(dt)
+            hourly_fy.append(fy_label)
+            hourly_proj_year.append(proj_year)
+
+            # Use full index into hourly arrays
+            idx = year * 8760 + hour_idx
+            solar_val = pipe.solar_hourly[idx] if pipe.solar_hourly and idx < len(pipe.solar_hourly) else 0.0
+            wind_val = pipe.wind_hourly[idx] if pipe.wind_hourly and idx < len(pipe.wind_hourly) else 0.0
+            total_re = solar_val + wind_val
+            hourly_total_re.append(total_re)
+            hourly_client_end.append(total_re * loss_factor)
+            hourly_load.append(client_load_mw)
 
     return ScenarioResult(
         inputs=inputs,