test: migrate stats/base/dists/gamma/mean 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 stats/base/dists/gamma/mean from relative tolerance assertions to ULP difference assertions, replacing the EPS-scaled delta <= tol checks in the fixture loops with isAlmostSameValue( y, expected[ i ], 1 ) in both test/test.js and test/test.native.js.
• drops the now-unused @stdlib/math/base/special/abs and @stdlib/constants/float64/eps requires and the associated delta/tol locals.

Final ULP constant: 1 (both test/test.js and test/test.native.js).

The bound was tightened from a high starting point down to the measured minimum. Over the full 200-value Julia fixture set (test/fixtures/julia/data.json), the maximum observed ULP difference is 1:

• 0 ULP → 45 of 200 fixture cases fail.
• 1 ULP → all cases pass.

So 1 is the minimum integer bound which passes, for both the JavaScript and the native implementation. Both implementations compute alpha / beta, which IEEE-754 rounds exactly, so the two produce bit-identical results across the fixture set (0 divergences measured) and share the same bound; no JS-vs-C split was required.

The package test suite (214 assertions per file) was run twice at the final bound, with the native add-on compiled so that test/test.native.js actually executes rather than skipping. Both runs were fully green, confirming there is no FMA/arch-dependent flakiness at 1 ULP.

Only the two test files are changed.

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.

The repository's editorconfig-checker pre-commit lint could not run in this environment, as the checker downloads its binary from the editorconfig-checker/editorconfig-checker GitHub releases, which is outside the network allowances available here. Formatting of the two changed files was instead verified manually (tab indentation, LF line endings, no trailing whitespace, single final newline). make lint-javascript-tests passes for both files.

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, running as an unattended scheduled task. It selected the package, mirrored the conversion idiom from already-merged PRs in the same family, measured the minimum ULP bound, and verified the tests and lint locally.

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@stdlib-js/reviewers

🤖 Generated with Claude Code

https://claude.ai/code/session_01Kzet3PR1rz8dncKtRLZ7eW

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/gamma/mean	$\\color{green}195/195$ $\\color{green}+100.00\\%$	$\\color{green}10/10$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}195/195$ $\\color{green}+100.00\\%$

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