test: migrate stats/incr/skewness 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 @stdlib/stats/incr/skewness from relative tolerance (EPS-scaled) assertions to ULP-based assertions using @stdlib/assert/is-almost-same-value, per [RFC]: Migrate math/base/special packages from relative tolerance testing to ULP difference testing (tracking issue) #11352.
• removes the now unused @stdlib/math/base/special/abs and @stdlib/constants/float64/eps requires, along with the associated delta/tol bookkeeping.

Only test/test.js is modified; the package has no test/test.native.js. No implementation, fixture, documentation, or benchmark changes are included.

ULP bounds

The package has two relative tolerance sites, covering four assertions in total:

Test	Previous tolerance	ULP	Measured minimum
the accumulator function incrementally computes a corrected sample skewness	1.5 * EPS	1	1
if not provided an input value, the accumulator function returns the current corrected sample skewness	EPS	1	1

Starting from 64 and tightening, 1 is the smallest bound which still passes. Every non-null expected value differs from the accumulated result by exactly one ULP:

Expected	Actual
1.457862967321305	1.4578629673213048
0.4366620845757488	0.43666208457574873
0.1171875	0.11718750000000001
1.986829609590966	1.9868296095909659

Re-running the suite at 0 fails exactly those 4 of 32 assertions, confirming 1 is the minimum. The suite was run twice at the final bound, passing 32/32 both times.

For reference, the sibling package stats/incr/nanskewness exercises the same expected values and also settled on 1.

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.

Verified locally with make test TESTS_FILTER=".*/stats/incr/skewness/.*" and make lint-javascript-tests TESTS_FILTER=".*/stats/incr/skewness/.*".

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 authored by Claude Code, which selected the package, studied already-migrated packages to match the established idiom, performed the migration, and searched for the minimum passing ULP bound by measurement.

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@stdlib-js/reviewers

🤖 Generated with Claude Code

https://claude.ai/code/session_01Vewx6nfMgR9fJUtfR1yJZg

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Coverage Report

Package	Statements	Branches	Functions	Lines
stats/incr/skewness	$\\color{green}181/181$ $\\color{green}+100.00\\%$	$\\color{green}14/14$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}181/181$ $\\color{green}+100.00\\%$

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