Function export_markdown 

pub fn export_markdown(
    session: &Session,
    params: Option<&[Parameter]>,
) -> String

Export a session as Markdown documentation.

Generates a Markdown document with:

• Session title
• Summary table (date, duration, command count, tags)
• Parameters table when parameters are provided
• Numbered steps with fenced code blocks
• Directory and exit code metadata per step

When params is Some, a parameters table is added after the summary and commands show {{VAR}} placeholders (Markdown passthrough).

Empty sessions produce a valid document with a “No commands recorded” note.