Feature: update_chapter tool and priority support for content ordering

[scocchiarella]

Summary

Two gaps prevent the MCP from controlling content order within a book:

1. update_page doesn't expose priority — only name, html, markdown, book_id, chapter_id are passed through
2. There is no update_chapter tool — chapters can be created and deleted but not renamed, reordered, or moved

BookStack displays book contents in priority order (chapters and top-level pages interleaved), so without priority access the MCP can build a book but can't control or fix its table of contents.

BookStack API support (verified against development branch)

Both PUT endpoints accept priority as an optional integer:

PUT /api/pages/{id} — already used by update_page, just needs priority added to the passthrough:

'priority' => ['integer'],

PUT /api/chapters/{id} — not currently exposed as a tool:

'name'                => ['string', 'min:1', 'max:255'],
'description'         => ['string', 'max:1900'],
'description_html'    => ['string', 'max:2000'],
'tags'                => ['array'],
'priority'            => ['integer'],
'book_id'             => ['integer'],   // moves chapter to another book
'default_template_id' => ['nullable', 'integer'],

There is no dedicated bulk "sort book" API endpoint — the UI's drag-and-drop uses an internal web route. Per-item priority via PUT is the supported API mechanism.

Proposed changes

1. update_page: add optional priority (integer, min 0)

Just add it to the input schema and pass it through — updatePage in the client already forwards the data object to axios unchanged.

2. New tool: update_chapter

Inputs:
  id: number (required)
  name: string (optional) — rename the chapter
  description: string (optional) — max 1900 chars
  priority: number (optional) — sort order within the book (lower = earlier)
  book_id: number (optional) — move chapter to another book
  tags: array (optional)

This also fixes the unrelated gap that chapters currently can't be renamed or have their description edited via MCP.

3. Client method: updateChapter(id, data)

Same pattern as updatePage:

async updateChapter(id, data) {
    if (!this.enableWrite) throw new Error('Write operations are disabled...');
    const response = await this.client.put(`/chapters/${id}`, data);
    return await this.enhanceChapterResponse(response.data);
}

Use case

We had a book where the chapter/page order didn't match the source document. Without priority access, the only fix was manual drag-and-drop in the BookStack UI. With these changes, the model can reorder an entire book's table of contents in a few tool calls.

We've implemented this in our fork and it's working. Happy to PR if you'd like.