feat: add fft/base/fftpack/ndarray/rffti

[gunjjoshi]

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Resolves stdlib-js/metr-issue-tracker#1070.

Description

What is the purpose of this pull request?

This pull request:

• adds fft/base/fftpack/ndarray/rffti, which will be the one-dimensional ndarry wrapper for fft/base/fftpack/rffti.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [RFC]: add fft/base/fftpack/ndarray/rffti metr-issue-tracker#1070

Questions

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No.

Other

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No.

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• Read, understood, and followed the contributing guidelines.

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Used Gemini 3.5 Flash to search and understand working of ndarray wrappers.

---

@stdlib-js/reviewers

[gunjjoshi]

Opening a draft PR to discuss the implementation here, since this seems to be a bit different from existing ndarray wrappers.

[gunjjoshi]

We can't directly send numelDimension( workspace, 0 ) here, as the length of the sequence to transform (N) is different from the size of the workspace array (2*N + 34).

[gunjjoshi]

@kgryte Let me know if the above looks good, or if I should make any changes here. I'll work on adding other files meanwhile.

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
fft/base/fftpack/ndarray/rffti	$\\color{green}143/143$ $\\color{green}+0.00\\%$	$\\color{green}3/3$ $\\color{green}+0.00\\%$	$\\color{green}1/1$ $\\color{green}+0.00\\%$	$\\color{green}143/143$ $\\color{green}+0.00\\%$

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

[gunjjoshi]

I have used ndarray here (for N) instead of something like int32ndarray, since I didn't saw a similar use anywhere.

[gunjjoshi]

Instead of using the full expected workspace array (which would be of length 2N+34), I have just initialized the twiddle and integer factors.

[gunjjoshi]

Since I am using these same 2 arrays in most of the tests, would it be better to move these to a separate // VARIABLES // section at the top? Or do we prefer this current way?