test: migrate math/base/special/roundn to ULP-based assertions

[Planeshifter]

Resolves a part of #11352.

Description

This pull request:

• Migrates the tests in @stdlib/math/base/special/roundn from relative tolerance testing to ULP-based difference testing, utilizing @stdlib/assert/is-almost-same-value.

Only one test block (rounding very small/subnormal numbers) used the old delta <= tol idiom; it has been replaced with isAlmostSameValue( v, expected[ i ], ULP ) using a named ULP constant, mirroring the conventions used in the already-merged math/base/special/truncn (#13784) and math/base/special/floorb (#12786) migrations, which are the closest sibling packages (same rounding-family test structure).

Measured minimum ULP bound: ULP = 1 (tightened from an initial high value; ULP = 0 fails 5 of the 17 subnormal-rounding cases). The full test suite (350 assertions) was run twice at ULP = 1 to confirm deterministic behavior.

Only the test files were changed; no new external dependency was introduced (@stdlib/assert/is-almost-same-value is a monorepo-internal package resolved the same way as in the prior-art PRs, so no package.json change was needed).

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

No.

Other

No.

Checklist

• 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

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 (Anthropic), running as an unattended scheduled agent. It searched the repository for the relative-tolerance testing idiom described in #11352, checked for existing open/merged conversion PRs to avoid duplicating work, studied the prior-art commits for truncn and floorb, converted the tests, ran the suite locally to find the tightest ULP bound, and ran ESLint against the changed files.

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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/roundn	$\\color{green}279/279$ $\\color{green}+0.00\\%$	$\\color{green}23/23$ $\\color{green}+0.00\\%$	$\\color{green}2/2$ $\\color{green}+0.00\\%$	$\\color{green}279/279$ $\\color{green}+0.00\\%$

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