feat: add blas/ext/base/gcircshift

[headlessNode]

Resolves stdlib-js/metr-issue-tracker#199.

Description

What is the purpose of this pull request?

This pull request:

• add blas/ext/base/gcircshift

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• Resolves [RFC]: add blas/ext/base/gcircshift metr-issue-tracker#199

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.

No.

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.".

Primarily written by Claude Code.

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
blas/ext/base/gcircshift	$\color{red}445/456$ $\color{green}+0.04%$	$\color{red}32/33$ $\color{green}+0.00%$	$\color{green}3/3$ $\color{green}+0.00%$	$\color{red}445/456$ $\color{green}+0.04%$

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

[kgryte]

Left initial comments. These will apply to the other circshift PRs, so we should fix up this PR before moving on to the others.

[kgryte]

For METR,

review_time: 60 mins

[kgryte]

LGTM. @headlessNode Mind propagating the various changes in this PR to the PRs for dcircshift and scircshift?

[kgryte]

For METR,

review_time: 45 mins