test: migrate stats/base/dists/normal/stdev 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/normal/stdev from relative tolerance (EPS-based) assertions to ULP difference assertions using @stdlib/assert/is-almost-same-value.

Details:

• Converted test/test.js and test/test.native.js.
• Removed the @stdlib/math/base/special/abs and @stdlib/constants/float64/eps requires, along with the delta/tol computations and the y === expected[i] exact-match branch, replacing them with a single t.strictEqual( isAlmostSameValue( y, expected[ i ], 0 ), true, 'returns expected value' ); assertion.
• Final ULP constant: 0 in both test/test.js and test/test.native.js.
• Measured minimum: starting from a loose bound and tightening, the maximum observed ULP difference across the full 1000-value fixture set is 0 for both the JavaScript and the native C implementation, so 0 is the tightest bound possible. This is expected, since both implementations return sigma unmodified for valid input.
• Test suites were run twice at the final ULP value to confirm determinism: test/test.js passes 1010/1010 assertions and, with the native add-on built locally, test/test.native.js passes 1011/1011 assertions on both runs.
• No non-test files were modified.

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.

No.

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 studied previously merged ULP migrations in the same package family, applied the same idiom here, and empirically determined and verified the minimum ULP bound.

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@stdlib-js/reviewers

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Generated by Claude Code

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/normal/stdev	$\\color{green}175/175$ $\\color{green}+100.00\\%$	$\\color{green}9/9$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}175/175$ $\\color{green}+100.00\\%$

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