test: migrate math/base/special/truncb 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/truncb from relative tolerance testing to ULP difference testing, as proposed in [RFC]: Migrate math/base/special packages from relative tolerance testing to ULP difference testing (tracking issue) #11352.
• replaces the delta/tol computation in the "very small numbers (including subnormals)" test with isAlmostSameValue( v, expected[ i ], 1 ), in both test/test.js and test/test.native.js.
• adds the @stdlib/assert/is-almost-same-value require and removes the now unused @stdlib/constants/float64/eps and @stdlib/math/base/special/abs requires.

The ULP bound was tightened to the measured minimum of 1 ULP for both the JavaScript and native test files. Over the 17 subnormal fixtures, 11 cases match exactly (0 ULP) and 6 cases require exactly 1 ULP (e.g. n = -308 returns 2.9999999999999997e-308 versus an expected 3e-308); no case requires more than 1, so 0 would fail and 1 is the tightest passing bound. The full test file was run twice at the final bound with identical results (766 passing assertions, no failures).

This matches the bound and idiom already used by the sibling packages math/base/special/floorb, math/base/special/ceilb, and math/base/special/truncn, which share the identical fixture set. Note that for b = 10 — the case exercised by this test — truncb delegates to truncn in both the JavaScript and C implementations, so the native path is expected to agree with the already-merged truncn native test at 1 ULP.

No implementation files were modified; the only changes are to the two test files.

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.

The native tests (test/test.native.js) were skipped locally, as the native add-on was not built in the environment used to author this change; npm install could not complete because the available registry mirror had no es-object-atoms@^1.1.2. The JavaScript tests were run directly and pass. Please confirm the native tests in CI.

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 unattended scheduled task. The conversion mirrors the already-merged floorb/ceilb/truncn migrations, and the 1 ULP bound was determined empirically by measuring the minimum passing ULP difference for every fixture rather than assumed.

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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/truncb	$\\color{green}203/203$ $\\color{green}+100.00\\%$	$\\color{green}24/24$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}203/203$ $\\color{green}+100.00\\%$

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