test: migrate math/base/special/gamma1pm1 to ULP-based assertions

[kgryte]

Resolves a part of #11352.

Description

What is the purpose of this pull request?

This pull request:

• migrates the tests for math/base/special/gamma1pm1 from relative tolerance (EPS-based) assertions to ULP difference assertions using @stdlib/assert/is-almost-same-value.
• updates both test/test.js and test/test.native.js, removing the now unused @stdlib/math/base/special/abs and @stdlib/constants/float64/eps requires.

The ULP bounds were tightened to the measured minimum which still passes over the full fixture sets:

Test case	Fixtures	Previous tolerance	ULP bound
small negative numbers	fixtures/cpp/small_negative.json (1000 values)	5.0 * EPS * abs( expected )	3
small positive numbers	fixtures/cpp/small_positive.json (1000 values)	2.0 * EPS * abs( expected )	2

The same bounds apply to both the JavaScript and the native (C) implementations, so test.js and test.native.js use identical values.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [RFC]: Migrate math/base/special packages from relative tolerance testing to ULP difference testing (tracking issue) #11352

Questions

Any questions for reviewers of this pull request?

No.

Other

Any other information relevant to this pull request? This may include screenshots, references, and/or implementation notes.

Notes on how the bounds were determined and verified:

• For each fixture value, the minimum N for which isAlmostSameValue( actual, expected, N ) returns true was computed; the bound above is the maximum such N over the full fixture set.
• The bounds are tight: lowering the small negative bound to 2 produces 1 failing assertion, and lowering the small positive bound to 1 produces 29 failing assertions.
• The native add-on was built locally (make install-node-addons NODE_ADDONS_PATTERN=gamma1pm1) so that test/test.native.js actually ran rather than being skipped.
• make test TESTS_FILTER=".*/math/base/special/gamma1pm1/.*" was run twice at the final bounds, with identical results each time (2691 passing in test.js, 2680 passing in test.native.js, 0 failing).
• make lint-javascript-tests TESTS_FILTER=".*/math/base/special/gamma1pm1/.*" is clean.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• Read, understood, and followed the contributing guidelines.

AI Assistance

When authoring the changes proposed in this PR, did you use any kind of AI assistance?

• Yes
• No

If you answered "yes" above, how did you use AI assistance?

• Code generation (e.g., when writing an implementation or fixing a bug)
• Test/benchmark generation
• Documentation (including examples)
• Research and understanding

Disclosure

If you answered "yes" to using AI assistance, please provide a short disclosure indicating how you used AI assistance. This helps reviewers determine how much scrutiny to apply when reviewing your contribution. Example disclosures: "This PR was written primarily by Claude Code." or "I consulted ChatGPT to understand the codebase, but the proposed changes were fully authored manually by myself.".

This PR was written by Claude Code, following the idiom established in previously merged conversions (e.g., math/base/special/sqrt1pm1, math/base/special/asec, math/base/special/powm1). The ULP bounds were measured empirically against the fixture sets rather than guessed.

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@stdlib-js/reviewers

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Generated by Claude Code

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/gamma1pm1	$\\color{green}551/551$ $\\color{green}+100.00\\%$	$\\color{green}62/62$ $\\color{green}+100.00\\%$	$\\color{green}6/6$ $\\color{green}+100.00\\%$	$\\color{green}551/551$ $\\color{green}+100.00\\%$

The above coverage report was generated for the changes in this PR.