Change titles to sentence case

[ethanpalm]

Documentation changes

This PR changes all page titles to sentence case. Sentence case is preferred for web content. It's more readable and generally looks better.

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For Reviewers

When reviewing documentation PRs, please consider:

✅ Technical accuracy

• Code examples work as written
• Commands and configurations are correct
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• Prerequisites and requirements are accurate

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• Nothing important is missing
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✅ User experience

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