docs: improve doctests for complex number instances in complex/base/cast-return

[aryan7071]

Resolves a part of #8641

Description

What is the purpose of this pull request?

This pull request:

• Updates REPL and documentation examples in the complex/base/cast-return package to use the compact complex instance doctest notation.
• Replaces example decomposition using realf/imagf with concise doctest annotations such as <Complex64>[ 7.0, 0.0 ].
• Removes example-only imports (realf, imagf) where they were only used to show decomposed values.
• Keeps all edits documentation-only (no runtime behavior or type changes).

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [RFC]: Improve doctests for complex number instances in documentation examples (tracking issue) #8641

(Replace the placeholder above with the relevant issue number if applicable.)

Questions

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No.

Other

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No.

Checklist

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AI Assistance

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@stdlib-js/reviewers

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[kgryte]

LGTM after considerable clean-up.

@aryan7071 Please ensure you have read and followed our contributing guidelines. It is clear from a number of mistakes made in this PR that you have not properly setup your local dev env.

[aryan7071]

Thank you for the feedback. I will review the contributing guidelines again and make sure my local dev env is set up correctly. I’ll follow the project’s conventions more closely in future contributions. Thank you for the guidance.