fix(binomial-distribution): compute pmf in log-space to avoid overflow - #182
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Integer arithmetic in choose(n:k:) crashes on overflow for large trial counts. Replace the coefficient calculation with logGamma arithmetic so the PMF is computed entirely in floating-point without intermediate integer overflow. Also adds boundary guards for p=0 and p=1 (preventing NaN from 0 × log(0)), a precondition on sample(_:), and expands the test suite with log-PMF cases, large-n cases, boundary-probability cases, and out-of-range x cases. Fixes: #176
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Integer arithmetic in choose(n:k:) crashes on overflow for large trial counts. Replace the coefficient calculation with logGamma arithmetic so the PMF is computed entirely in floating-point without intermediate integer overflow.
Also adds boundary guards for p=0 and p=1 (preventing NaN from 0 × log(0)), a precondition on sample(_:), and expands the test suite with log-PMF cases, large-n cases, boundary-probability cases, and out-of-range x cases.
Fixes: #176