Fix panic when sorting prices containing NaN in test

[aviu16]

Summary

Fixes a potential panic in the smallest_positive_gap test helper function when input prices contain NaN values.

Bug Description

In exchange/src/adapter/hyperliquid.rs, the smallest_positive_gap function panics when sorting prices that contain NaN:

fn smallest_positive_gap(mut prices: Vec<f32>) -> Option<f32> {
    prices.sort_by(|a, b| b.partial_cmp(a).unwrap());  // Panics if a or b is NaN!
    // ...
}

The partial_cmp method returns None when comparing NaN values (per IEEE 754 floating point spec), causing .unwrap() to panic.

Root Cause

Using .unwrap() on partial_cmp without handling the NaN case.

Fix

Changed to .unwrap_or(std::cmp::Ordering::Equal) to treat NaN values as equal during sorting:

prices.sort_by(|a, b| b.partial_cmp(a).unwrap_or(std::cmp::Ordering::Equal));

This prevents the panic while maintaining correct sort behavior for valid numbers.

Impact

• This is currently only used in test code (#[cfg(test)] module)
• Makes the code more defensive against unexpected NaN inputs
• No change in behavior for valid floating point inputs

Testing

The fix ensures that if test data ever contains NaN values (e.g., from invalid price feeds or calculation errors), the test helper won't panic.

[aviu16]

closing this for now, gonna revisit later