Module derive 

Derived metric computation for analytics buckets.

All division operations are safe against zero denominators and produce None (rendered as JSON null) rather than NaN / Infinity.

Functions

compute_derived

Compute all derived metrics from a UsageBucket.

safe_div

Safe division returning None when the denominator is zero.

safe_div_f64

Safe division for f64 numerator with i64 denominator. Returns None when the denominator is zero.

safe_pct

Percentage safe against zero denominator. Returns 0.0 when denominator is zero. Result is rounded to 2 decimal places (matching the original CLI rounding: (pct * 100.0).round() / 100.0).