docs: improve doctests for ndarray instances in ndarray/slice-from

[Thanatos9404]

Progresses #9329.

Description

What is the purpose of this pull request?

This pull request:

• Updates the README, REPL text, TypeScript declarations, and JSDoc examples in @stdlib/ndarray/slice-from to replace ndarray2array decomposition logic with ndarray instance notation (e.g., // returns <ndarray>[ [ 3.0, 4.0 ], [ 5.0, 6.0 ] ]).
• Removes the @stdlib/ndarray/to-array import wherever it was only used to show expected values.
• Leaves examples/index.js unchanged, as that file intentionally prints nested arrays.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [RFC]: Improve doctests for ndarray instances in documentation examples (tracking issue) #9329

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.

The changes follow the same pattern as the ndarray/slice update in #14771. In the strict: false README example, which returns an empty view, the annotation stays // returns <ndarray> (as in ndarray/slice). The complex number examples in docs/types/index.d.ts only drop the unused import.

Every updated annotation was checked locally with the project's own doctest rules (stdlib/jsdoc-doctest for lib/*.js, stdlib/tsdoc-declarations-doctest for docs/types/index.d.ts, the _tools/repl-txt doctest rule for docs/repl.txt, and stdlib/doctest for the README code blocks). The package unit tests also pass (440/440).

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.".

Drafted with Claude Code, following the pattern from #14771; every annotated return value was checked against stdlib's doctest rules.

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