Extract token-type and per-model cost calculations from cmd/costs.go
into a dedicated pipeline.AggregateCostBreakdown() function. This
eliminates duplicate cost calculation logic between CLI and TUI.
New types:
- TokenTypeCosts: aggregate costs by input/output/cache types
- ModelCostBreakdown: per-model cost components
Benefits:
- Single source of truth for cost calculations
- Uses LookupPricingAt() for historical accuracy
- Both CLI and TUI now share the same cost logic
- Easier to maintain and extend
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
