test: migrate stats/base/dists/planck/cdf to ULP-based assertions

[kgryte]

Resolves a part of #11352.

Description

What is the purpose of this pull request?

This pull request:

• Migrates the unit tests for @stdlib/stats/base/dists/planck/cdf from relative tolerance checks (delta <= tol, computed as 1.0 * EPS * abs( expected[ i ] )) to ULP-based assertions using @stdlib/assert/is-almost-same-value.
• Applies the migration to test/test.cdf.js, test/test.factory.js, and test/test.native.js (the three files containing fixture loops with computed tolerances). test/test.js only performs exact comparisons and is left unchanged.
• Removes the now-unused @stdlib/math/base/special/abs and @stdlib/constants/float64/eps requires, along with the delta and tol declarations.

ULP bounds

The bounds are the measured minima over the full fixture sets, determined by computing the maximum ULP difference between the actual and expected values for every fixture element:

Fixture	ULP bound	Notes
small_lambda.json	1	Max measured ULP difference is exactly 1 (a single element, x = 1, lambda ≈ 0.0431137); 0 fails.
large_lambda.json	0	All 1000 elements match exactly; 0 is the minimum possible.

The same bounds are used in test.cdf.js, test.factory.js, and test.native.js.

Verification

• Package tests are green, and the suite was run twice at the final bounds with identical results (2010 + 2014 + 3 assertions passing; test.native.js is skipped, as the native add-on is not built in this environment).
• Minimality was confirmed programmatically: lowering the small-lambda bound to 0 fails for both the main and factory implementations, while 1 passes.
• make lint-javascript-files ... ESLINT_CONF=etc/eslint/.eslintrc.tests.js is clean.
• Only the three test files are changed.

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?

• The test.native.js bounds mirror the JavaScript bounds, following the convention in already-converted packages (e.g., stats/base/dists/poisson/cdf), but could not be measured here because the native add-on was not built. Please flag if you would prefer them verified against a built add-on first.

Other

Any other information relevant to this pull request? This may include screenshots, references, and/or implementation notes.

The inline integer bound idiom (rather than a named ULP constant) mirrors the prevailing convention in stats/base/dists, where all already-converted test files use inline literals.

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 authored by Claude Code, which surveyed prior converted packages to match the established idiom, applied the test edits, and measured the minimum ULP bounds empirically over the fixture sets.

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@stdlib-js/reviewers

🤖 Generated with Claude Code

https://claude.ai/code/session_015ih3rRmRJdoJ4wWMPTY83i

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Generated by Claude Code

[stdlib-bot]

Hello! 👋

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/planck/cdf	$\\color{green}279/279$ $\\color{green}+100.00\\%$	$\\color{green}25/25$ $\\color{green}+100.00\\%$	$\\color{green}4/4$ $\\color{green}+100.00\\%$	$\\color{green}279/279$ $\\color{green}+100.00\\%$

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