test: migrate math/base/special/croundn 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/croundn from relative tolerance testing to ULP difference testing.
• replaces the delta/tol relative error comparison in test/test.js and test/test.native.js with isAlmostSameValue( actual, expected[ i ], 1 ) assertions, adding the @stdlib/assert/is-almost-same-value require and dropping the now unused @stdlib/constants/float64/eps and @stdlib/math/base/special/abs requires.

The affected test is the function supports rounding very small numbers (including subnormals), which compares both the real and imaginary components against the expected fixture values.

ULP constants used:

File	ULP
test/test.js	1
test/test.native.js	1

Both values were tightened to the measured minimum: the maximum observed ULP difference over the full fixture set is 1 for the JavaScript implementation and 1 for the native implementation, and re-running the suite with a bound of 0 fails 10 assertions in each file. The suite was run twice at the final bound to confirm the results are deterministic (690 passing in test/test.js, 684 passing in test/test.native.js, with the native add-on compiled locally so that the native tests actually execute rather than skip).

Only the two test files are 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

This PR was authored by Claude Code running as an automated task. The ULP bounds were measured empirically against the existing fixtures 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/croundn	$\\color{green}176/176$ $\\color{green}+100.00\\%$	$\\color{green}5/5$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}176/176$ $\\color{green}+100.00\\%$

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