Markdown export does not preserve original formatting (indentation, list markers, and horizontal rules)

Bug Report

Problematic behavior

When exporting a document to Markdown, the exported content does not preserve the original Markdown syntax:

• leading tabs and spaces at the beginning of blocks are removed
• unordered lists using - are converted to *
• horizontal separators written as --- are converted to ***

Expected behavior/code

The Markdown export should preserve the original Markdown formatting exactly as written in the editor, including:

• leading tabs and spaces
• list markers (- should remain - )
• horizontal rules (--- should remain ---)

Steps to Reproduce

1. Create a document containing:
   • indented lines using spaces or tabs
   • unordered lists using -
   • horizontal rules using ---
2. Export the document as Markdown
3. Open the exported .md file
4. Notice that indentation is removed, list markers are changed to * , and separators are converted to ***

Environment

• Instance url: https://docs.numerique.gouv.fr/