Summary

Add an optional PDF-focused enhancement to the GUI wrapper so PDF conversions can preserve extracted images, preview them before save, and optionally use a PyMuPDF-based PDF pipeline while keeping MarkItDown as the default behavior.

Scope

• Keep the GUI as a wrapper of MarkItDown by default.
• Add a PDF pipeline toggle: markitdown or pymupdf.
• Add optional PDF image preservation in Markdown.
• Support asset layouts separate and single, independent from combined/separate Markdown save mode.
• Preserve preview/save flows and batch conversion behavior.

Acceptance Criteria

• Non-PDF formats keep existing behavior.
• PDFs keep existing behavior when image preservation is disabled.
• PDFs can preserve extracted images as files and link them from Markdown.
• The rendered preview can resolve extracted PDF image assets before save.
• The pymupdf pipeline can place extracted images near the closest preceding text block on a best-effort basis.
• Combined and separate save modes both rewrite image links correctly.
• Test coverage includes conversion routing, runtime UI paths, real generated PDFs, and packaging smoke coverage.