Split Language Detection page into "Automatic language detection" and "Set language manually" pages

[devin-ai-integration]

Summary

Replaces the single "Language detection" page in the Pre-recorded Speech-to-Text navigation with a new "Languages" section containing two separate pages:

• Automatic language detection (automatic-language-detection.mdx)
• Set language manually (set-language-manually.mdx)

Both target MDX files already exist in the repo. The section uses skip-slug: true so URLs nest directly under the parent path.

Review & Testing Checklist for Human

• Verify no broken links: The old URL /docs/pre-recorded-audio/language-detection will no longer resolve. Check whether a redirect is needed (e.g., in pre-recorded-audio-redirect.js) to avoid breaking existing inbound links or cross-references within the docs.
• Verify content completeness: The original language-detection.mdx contained sections on automatic detection, expected languages, fallback language, confidence score/threshold, manual language setting, and supported languages. Confirm that automatic-language-detection.mdx and set-language-manually.mdx collectively cover all of this content.
• Preview the deployed docs: After merge, verify the new "Languages" section renders correctly in the sidebar under Pre-recorded Speech-to-Text and both pages load properly.

Notes

• Link to Devin run
• Requested by @LeeVaughn

[devin-ai-integration]

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