Technical diagrams can now stay inside the Markdown document and remain comfortable to edit.
What changed
- Edit Mermaid source and see the rendered diagram update beside it.
- Keep source and preview aligned on wide screens.
- Stack both panes on narrow screens without horizontal overflow.
- Use the document theme when rendering light and dark diagrams.
- Save standard Mermaid Markdown that remains readable outside Letter.md.
Invalid source stays editable and shows an error without replacing the last useful diagram.