Remove redundant top-level H1 headings and normalize page titles

[Blargian]

Motivation

• Clean up documentation source files by removing duplicated top-level headings that are already provided via frontmatter to avoid rendering duplicate titles and improve consistency.
• Normalize a small number of frontmatter title values and inline titles for consistency and correct formatting.

Description

• Removed redundant # <Title> H1 lines from many markdown files so the site uses the frontmatter title (or hide_title) consistently.
• Adjusted select frontmatter titles and inline text for consistency, including adding code formatting to OPTIMIZE FINAL and minor capitalization/wording changes (for example, DataStore I/O operations → Datastore I/O operations, and changelog titles lowercased).
• Kept all existing frontmatter and content structure intact aside from the removed H1 lines and the few targeted title edits.

Testing

• Built the documentation site with yarn build to verify no rendering errors and ensure titles render from frontmatter, and the build completed successfully.
• Ran markdownlint over the modified files to validate markdown style and found no lint failures.
• Performed a quick local link/preview pass to confirm pages render and navigation remains intact.

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Codex Task

[vercel]

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Project	Deployment	Actions	Updated (UTC)
clickhouse-docs	Ready	Preview, Comment	May 11, 2026 3:51pm

3 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
clickhouse-docs-ko	Ignored	Preview	May 11, 2026 3:51pm
clickhouse-docs-ru	Ignored	Preview	May 11, 2026 3:51pm
clickhouse-docs-zh	Ignored	Preview	May 11, 2026 3:51pm