test: migrate math/base/special/atand to ULP-based testing

[Planeshifter]

Resolves a part of #11352.

Description

What is the purpose of this pull request?

This pull request:

• migrates test/test.js and test/test.native.js of math/base/special/atand from relative-tolerance (EPS-based) assertions to ULP-difference assertions via @stdlib/assert/is-almost-same-value, using the minimum required ULP values (verified by direct ULP-difference computation over the test fixtures).
• removes the now-unused abs and EPS requires and the obsolete delta/tol variables, and collapses the exact-equality short-circuit branches into the single isAlmostSameValue assertion.

Both fixture blocks (negative.json, positive.json) require a minimum of 1 ULP for both the JavaScript and native (C) implementations; the native results matched the JavaScript results in ULP terms, so no tolerance divergence comment was needed. JavaScript and native test suites both pass (4009/4009 assertions each).

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.

Minimality of the ULP values was verified by recomputing the maximum ULP difference over all fixture values (a tolerance of 0 ULP fails 6 assertions in the JavaScript test suite).

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 written by Claude Code, which performed the test migration, computed the minimum ULP tolerances, and independently verified the results; the changes were reviewed by a human before submission.

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@stdlib-js/reviewers

[stdlib-bot]

Hello! 👋

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/atand	$\\color{green}188/188$ $\\color{green}+100.00\\%$	$\\color{green}5/5$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}188/188$ $\\color{green}+100.00\\%$

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