Fix capitalization and TOC structure in campaign docs

[Copilot]

Campaign documentation had inconsistent capitalization ("Agentic Campaigns" vs "agentic campaigns") and duplicate headings across files that confused navigation.

Changes

Capitalization standardization:

• Page titles and headings: Title case → sentence case ("Campaign Commands" → "Campaign commands")
• Feature references: Capitalized → lowercase ("Agentic Campaigns" → "agentic campaigns")
• Internal link text updated to match new heading format

TOC deduplication:

• index.mdx: "How it works" → "Workflow" (avoids collision with technical-overview.md)
• index.mdx: "What are GitHub Agentic Campaigns?" → "Overview" (clearer, more concise)

Before/After

  ---
- title: "CLI Commands"
+ title: CLI commands
  ---

- ## Campaign Commands
+ ## Campaign commands

- See [Project Management](/gh-aw/guides/campaigns/project-management/)
+ See [Project management](/gh-aw/guides/campaigns/project-management/)

All 7 campaign doc files updated. Frontmatter, internal links, and markdown syntax validated.

Original prompt

Fix capitalization in campaign docs. Also, make sure toc makes sense and don't duplicate titles, etc.

Custom agent used: technical-doc-writer
AI technical documentation writer for GitHub Actions library using GitHub Docs voice

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