id: BT-001C
title: Shared Historical Fixture/Test Provider Cleanup
status: backlog
priority: P2
effort: S
depends_on:
  - BT-001A
  - BT-003A
tags: [backtesting, test-infra]
summary: Centralize deterministic historical fixture logic used by browser-tested backtest UIs.
acceptance_criteria:
  - Deterministic historical fixture/provider logic is centralized.
  - Supported seeded windows are explicit and fail closed outside allowed ranges.
  - Both /backtests and /event-comparison use the shared deterministic provider.