Issue #199: 章slug整理＋旧URL誘導（第3〜7章）

[ootakazuhiko]

Closes #199

変更概要

• 第3〜7章の slug（ディレクトリ名）を章題/内容に合わせて整理
  • chapter-github-account-setup → chapter-repository-creation
  • chapter-basic-operations → chapter-account-security
  • chapter-repository-management → chapter-file-management
  • chapter-collaboration-basics → chapter-github-desktop
  • chapter-pull-requests → chapter-branch-operations
• 旧URL誘導（方針A）
  • 旧slug側の docs/chapters/<old>/index.md を「移動しました」ページとして追加
• 公開サイト側の導線更新
  • docs/_data/navigation.yml / docs/index.md のパスを新slugへ更新
  • Pull Request章参照などの章内リンクを新slugへ更新
• エージェント用対応表更新
  • AGENTS.md の slug→章対応表を更新

動作確認（ローカル）

• npx markdownlint ...（変更Markdown）
• python3 scripts/check_markdown_internal_links.py ...（変更Markdown）
• python3 scripts/check_bidi_unicode.py

補足

• 旧URLは自動リダイレクトではなく「移動案内ページ」で新URLへ誘導します（Jekyll追加プラグイン依存を避けるため）。

[Copilot]

Pull request overview

This PR reorganizes chapter slugs (directory names) for chapters 3-7 to align with actual chapter titles and content, addressing the mismatch identified in Issue #199. The PR implements old URL redirection using static "moved" pages (方針A) to guide users from old URLs to new locations.

Changes:

• Renamed 5 chapter directories to match chapter titles (e.g., chapter-github-account-setup → chapter-repository-creation)
• Added redirect pages at old slug locations directing users to new URLs
• Updated all navigation files, internal links, and the AGENTS.md mapping table

Reviewed changes

Copilot reviewed 20 out of 25 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
manuscript/chapter-repository-creation/index.md	New location for Chapter 3 content
manuscript/chapter-account-security/	New location for Chapter 4 (not shown but implied)
manuscript/chapter-file-management/index.md	New location for Chapter 5 content
manuscript/chapter-github-desktop/index.md	New location for Chapter 6 content
manuscript/chapter-branch-operations/index.md	New location for Chapter 7 content
docs/chapters/chapter-github-account-setup/index.md	Redirect page for old Chapter 3 URL
docs/chapters/chapter-basic-operations/index.md	Redirect page for old Chapter 4 URL
docs/chapters/chapter-repository-management/index.md	Redirect page for old Chapter 5 URL
docs/chapters/chapter-collaboration-basics/index.md	Redirect page for old Chapter 6 URL
docs/chapters/chapter-pull-requests/index.md	Redirect page for old Chapter 7 URL
docs/chapters/chapter-repository-creation/index.md	New published location for Chapter 3
docs/chapters/chapter-file-management/index.md	New published location for Chapter 5
docs/chapters/chapter-github-desktop/index.md	New published location for Chapter 6
docs/chapters/chapter-branch-operations/index.md	New published location for Chapter 7
docs/_data/navigation.yml	Updated navigation paths to new slugs
docs/index.md	Updated chapter links to new slugs
manuscript/chapter-issue-management/index.md	Updated internal reference to Chapter 7
manuscript/chapter-docs-as-code/index.md	Updated internal reference to Chapter 7
docs/chapters/chapter-issue-management/index.md	Updated internal reference to Chapter 7
docs/chapters/chapter-docs-as-code/index.md	Updated internal reference to Chapter 7
manuscript/chapter-team-development/index.html	Updated redirect to new Chapter 6 location
manuscript/chapter-github-account/index.html	Updated redirect to new Chapter 3 location
project-management/structure-review-round1.md	Updated slug references in documentation
AGENTS.md	Updated slug-to-chapter mapping table

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