feat(openquant): add AFML ch15 strategy risk diagnostics

[Sean-Koval]

Summary

• add AFML Chapter 15 strategy risk diagnostics module
• include symmetric/asymmetric Sharpe utilities and implied precision/frequency helpers
• add strategy failure probability estimation workflow and tests
• wire module/docs references

Validation

• cargo test -p openquant --test strategy_risk
• cargo test -p openquant --lib --tests
• cargo clippy --all-targets --all-features -- -D clippy::correctness -D clippy::suspicious