test: migrate math/base/special/coth 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 in math/base/special/coth 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 all test fixtures: the data fixture requires a maximum ULP of 2; the tiny_negative, tiny_positive, large_negative, and large_positive fixtures match exactly and thus use plain t.strictEqual.
• 2 was confirmed to be the tightest bound (an ULP of 1 produces failures across the data fixture); the test suite was run twice at the final bound to confirm no flakiness.

The native (C) addon could not be built/exercised in this environment (no prebuilt addon present and native module builds are unavailable here), so test.native.js was updated to mirror the same tolerances as test.js, consistent with the precedent set by prior conversions of the closely-related sinh/csch packages, which found no JS-vs-C divergence for this class of function.

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 written primarily by Claude Code (running as an unattended scheduled task), including the test migration and the computation/verification of minimum ULP tolerances directly against the fixtures.

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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/coth	$\\color{green}164/164$ $\\color{green}+100.00\\%$	$\\color{green}5/5$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}164/164$ $\\color{green}+100.00\\%$

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