Fix: nb default space

[docxology]

[Verified audit fix] — branch fix/nb-default-space.

Commit: fix(NegativeBinomial): repair DefaultParametersSpace helpers

Changes

src/distributions/negative_binomial.jl | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

Verification

Confirmed against main in the ReactiveBayes audit (Julia 1.12.6); sources verified read-only. See the branch diff.

[bvdmitri]

Confirmed, all three defects:

• !isnan(p) && !isinf(p) && (1 => p > 0) — the 1 => p > 0 is a Pair, always truthy, so p > 0 was never enforced.
• the gradient closure referenced an undefined η (its arg is θ) — an UndefVarError crash.
• default-space -r·log(1-p) disagreed with natural-space -r·log(p).

All three fixes are correct. Pushed a regression test covering the Bool return, default-vs-natural agreement, and the gradient.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.06%. Comparing base (a72e447) to head (b76493f).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #306      +/-   ##
==========================================
+ Coverage   83.91%   84.06%   +0.14%     
==========================================
  Files          45       45              
  Lines        4078     4078              
==========================================
+ Hits         3422     3428       +6     
+ Misses        656      650       -6     

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