Goal: v1 prototype shippable. Real-world bid prep ready.
Tasks:

 S8-T01 scenarios/sweep.py: Cartesian sweep engine. Parallel via Arq.
 S8-T02 Predefined sensitivities (the "frequent 7"). One-click from results page.
 S8-T03 Tornado chart (Recharts).
 S8-T04 Custom sweep UI: pick params, ranges, steps. DataGrid for results table.
 S8-T05 Side-by-side comparison view: pick 2-4 scenarios, KPI diff, statement diff.
 S8-T06 io/excel_export.py: full statements + KPIs + inputs to multi-sheet xlsx using openpyxl.
 S8-T07 Bug bash: run 5 historical bids. Document discrepancies.
 S8-T08 Performance pass: target <30s for single scenario, <10min for 50-scenario sweep.
 S8-T09 README polish, screenshots, demo recording.
 S8-T10 Final parity validation: all 5 historical bids within 0.5%.

Definition of Done: v0+v1 ready for production bid prep. Excel can be deprecated for solar+wind+BESS hybrid RTC.