feat: add @stdlib/string/base/truncate-middle-code-points

[ujjwalv01]

Resolves part of #1062

Description

What is the purpose of this pull request?

This pull request:

• Adds the @stdlib/string/base/truncate-middle-code-points package.
• Implements a base utility function that truncates a string in the middle to a specified length based on Unicode code points.
• This ensures that when truncating strings containing characters comprised of more than one Unicode code unit (e.g., emoji, ideographic symbols), surrogate pairs are not split in half, which prevents malformed output.
• Serves as a foundational piece for updating the top-level @stdlib/string/truncate-middle package to support different modes.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• Part of Tracking issue: refactor string packages handling grapheme clusters in terms of "base" packages #1062

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.".

I utilized an AI assistant to automate the generation of test cases (specifically handling complex emoji surrogate pairs) and benchmark scaffolding. The core logic implementation and integration were authored manually.

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@stdlib-js/reviewers

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
string/base/truncate-middle-code-points	$\\color{green}134/134$ $\\color{green}+100.00\\%$	$\\color{green}9/9$ $\\color{green}+100.00\\%$	$\\color{green}1/1$ $\\color{green}+100.00\\%$	$\\color{green}134/134$ $\\color{green}+100.00\\%$

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

[ujjwalv01]

Closing this PR in favor of #13782 , which consolidates all three packages (truncate-middle-code-points, truncate-middle-grapheme-clusters, and the top-level truncate-middle refactor) into a single PR for easier review. All changes from this PR are included there.

[kgryte]

Reopening, as our preference is that PRs adding new packages only contain a single package.

[ujjwalv01]

Thanks for reopening! These are up-to-date and ready for review.