Extend Section with TOC boundary tracking: buildTocBoundaries(),
getTocIndexForPage(), getPageForTocIndex(), getPageRangeForTocIndex(),
readAnchorMap(), and readCachedPageCount() for lightweight cache queries.
ChapterHtmlSlimParser now accepts a tocAnchors set and forces page breaks
at TOC anchor boundaries so each chapter starts on a fresh page.
Increment SECTION_FILE_VERSION to 19 for new TOC boundary data.
Ported from upstream PRs #1143 and #1172, adapted to mod architecture.
Made-with: Cursor
f2a2b03074
