Continue Development Work

[skyelaird]

Critical Fixes:

1. Fix NaN in _cos_of_incidence() - added guard for negative sqrt values
2. Fix NaN in ground reflection loss - clamp sqrt arguments to non-negative
3. Fix reference parser reading wrong columns - capture values before metric names

Before: All predictions returned NaN for loss/SNR/power
After: Valid predictions with SNR within 10-21 dB of reference (except high freq)

Remaining Issues:

• SNR still 10-21 dB too low (loss too high by same amount)
• High frequencies (>15 MHz) not finding modes

Test Results:

• 1/9 tests passing for hour 1
• No more NaN values
• No more sqrt warnings