feat: add C implementation for stats/base/dists/chi/skewness

[rautelaKamal]

Description

What is the purpose of this pull request?

This pull request:

• Adds a C implementation for @stdlib/stats/base/dists/chi/skewness.
• Adds N-API bindings to expose the C implementation to Node.js.
• Refactors the JavaScript implementation to fallback safely to pure JS if the native module fails to load.
• Updates documentation and includes standalone C benchmarks and examples.

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

Other

No.

---

@stdlib-js/reviewers

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Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/chi/skewness	$\color{green}172/172$ $\color{green}+100.00%$	$\color{green}8/8$ $\color{green}+100.00%$	$\color{green}2/2$ $\color{green}+100.00%$	$\color{green}172/172$ $\color{green}+100.00%$

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

[Planeshifter]

Please do not open AI-generated PRs without double-checking what you are submitting and be transparent in disclosing usage of AI assistance. As you can see, the C implementation already exists, so this PR shouldn't have been opened.

[rautelaKamal]

Please do not open AI-generated PRs without double-checking what you are submitting and be transparent in disclosing usage of AI assistance. As you can see, the C implementation already exists, so this PR shouldn't have been opened.

Thank you for the review and for catching this, @Planeshifter. I sincerely apologize for wasting your time. You are completely right on both counts.

To be transparent: I have been using an AI assistant to help me learn the codebase structure and draft boilerplate for these implementations. In my eagerness to get a PR up, I became completely focused on getting the CI checks (linting, exports, tests) to pass for the new code I was generating. In doing so, I completely failed to do the most important step: checking the develop branch to see if the C implementation for chi/skewness was already there.

The multiple commits were my sincere (but misguided) attempts to satisfy the CI, not an attempt to spam the repo.

I take your feedback very seriously. Going forward, my protocol will be:

I will manually verify against the latest develop branch that an implementation doesn't already exist before writing a single line of code.
I will explicitly disclose my use of AI assistance in my PR descriptions, as you requested.
I will double-check that I fully understand the code being submitted, rather than blindly following the AI's lead.
Thank you for the reality check. I will be much more careful and deliberate with future contributions.