v0.66.0

Minor Changes

• Expand a Mermaid diagram to a full-screen viewer.

  Diagrams render inline at the width of the prose column, which is rarely the width a flowchart wants. A rendered diagram can now open in a full-screen dialog — from the expand control in its pan/zoom toolbar, or from the block's hover chrome beside Edit source. The viewer is view-only, has its own pan/zoom controls with trackpad panning and pinch-to-zoom, tracks live edits to the underlying chart, and closes with Escape or the close button, returning to the inline diagram untouched.