Printing is broken in Firefox

[seshrs]

When I try to print a Primer Spec page in Firefox v99.0.1 on MacOS:

• The main content margin isn't reset.
• Mermaid diagrams still appear in dark colors (if the current color mode is "dark").

Printing works fine in Chrome and Safari. I'm not yet sure if this is a Firefox browser bug or if this is a gap in the HTML standards... and I'm not yet sure how to work around the issue either.