fix: preserve sign in math/base/special/{ceil2,floor2}

[Planeshifter]

Description

What is the purpose of this pull request?

This pull request:

• propagates fixes merged to develop between 2026-09-29 and 2026-09-30 to sibling packages.
• propagates 85d7c62 ("fix: preserve sign"), which fixed round2 returning the absolute value of the input when provided the negative smallest subnormal. ceil2 and floor2 share the same early return, in both the JavaScript and C implementations: ceil2( -SMALLEST_SUBNORMAL ) and floor2( -SMALLEST_SUBNORMAL ) currently return +SMALLEST_SUBNORMAL. The JavaScript implementations now return sign * x and the C implementations return x, matching round2. The added tests mirror the one added in 85d7c62.
  • @stdlib/math/base/special/ceil2
  • @stdlib/math/base/special/floor2

Related Issues

Does this pull request have any related issues?

No.

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 search covered every lib/main.js and src/main.c under math/base/special/* that has a smallest-subnormal early return. Siblings that were checked and are already correct: round2 (JS), floor2f, round10, ceil10, floor10.

Other source commits in the window had no remaining sites to fix:

• fb5ec21 (NaN macro parentheses): no other STDLIB_CONSTANT_* macro is an unparenthesized compound expression.
• ec5c016 (enum doc example, benchmark values): the sibling ml/base/sgd enums and resolve benchmarks are already correct.
• d374b24 (strictEqual( ( a === b ), true )): no remaining occurrences.

Validation: an independent review read each file in full and confirmed each site. The JS tests were run before and after the fix. Native builds were not available, so the C changes were not compiled or run.

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

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• Code generation (e.g., when writing an implementation or fixing a bug)
• Test/benchmark generation
• Documentation (including examples)
• Research and understanding

Disclosure

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This PR was written primarily by Claude Code as part of an automated fix-propagation routine.

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Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/ceil2	$\\color{green}193/193$ $\\color{green}+100.00\\%$	$\\color{green}19/19$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}193/193$ $\\color{green}+100.00\\%$
math/base/special/floor2	$\\color{green}193/193$ $\\color{green}+100.00\\%$	$\\color{green}19/19$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}193/193$ $\\color{green}+100.00\\%$

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