Intercept 'mermaid' code blocks in render.rs and call
mermaid::render_diagram() to convert to inline SVG.
- Use catch_unwind to handle upstream dagre_rust panics gracefully
- Graceful fallback: show raw code with mermaid-error class on failure
- Flowcharts render correctly; some diagram types hit upstream bugs
Add src/mermaid.rs with render_diagram() wrapper around
mermaid-rs-renderer for build-time Mermaid-to-SVG conversion.
- Use mermaid-rs-renderer git dependency (SVG-only, no PNG)
- Configure with RenderOptions::modern() theme
- Include unit tests for flowchart and sequence diagrams