Add automatic chapter renumbering when chapters are reordered

[bob-duetto]

Feature Request

Description:
When reorganizing a book (moving, adding, or removing chapters), chapter numbers in titles need to be manually updated. This is error-prone and tedious.

Requested Feature:
Add a tool or option to automatically renumber chapters based on their position in SUMMARY.md. Options could include:

1. A new MCP tool renumber_chapters that updates chapter title prefixes based on position
2. An option in update_toc to also update chapter number prefixes in titles
3. A chapter_numbering config option in book.toml that controls numbering format (e.g., "1.", "Chapter 1:", "1.1", etc.)

Use Case:
When writing a book, chapters frequently get reorganized. Currently, if I move Chapter 5 to position 3, I need to manually update:

• The title in SUMMARY.md
• The H1 heading in the chapter file
• Any cross-references to that chapter

Suggested Implementation:

• Parse SUMMARY.md for chapter order
• Update H1 headings in chapter files to match position
• Support configurable number formats (numeric, roman numerals, etc.)
• Optionally update cross-references

Related:

• Core mdbook doesn't support this either
• Third-party preprocessors exist (mdbook-numbering, mdbook-chapter-number) but require separate installation