Maps the design doc (commit 280f807) to bite-sized tasks. Phase 1 ships
strategy + backtest + bridge in audit-only mode; Phase 2 extends
OrderRequest/AlpacaBroker for BRACKET orders, extends RiskManager, and
flips the kill-switch; Phase 3 ships the paper-account UI page.
Each task has Test → Run-and-fail → Implement → Run-and-pass → Commit
steps with concrete code in every step. Implementer can pick up any
task without prior session context.