docs(v3): update /api/index

[NoiseFan]

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描述

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[Copilot]

Pull request overview

This PR updates the v3 API index documentation (/api/index) to improve Chinese translation accuracy and readability, primarily by refining phrasing and translating previously-English inline descriptions.

Changes:

• Refined wording/spacing in several API descriptions (e.g., test.only).
• Localized inline comments and option descriptions in code examples (e.g., test.concurrent combinations, test.each printf specifiers).
• Adjusted several example comments for more natural Chinese phrasing.

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[thinkasany]

@codex

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Bravo.

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[thinkasany]

@codex

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 🚀

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