Mermaid v10+ renders \n as literal text in node labels. Replace all
152 occurrences across 28 files with <br/> which produces proper
line breaks in the rendered diagrams.
This fixes technical accuracy issues, most notably in the C# book.
There are other minor tweaks, including simplying technical jargon in the
type-drive-correctness book.
- Retarget C# companion links from missing source-docs paths to book SUMMARYs.
- Fix type-driven correctness intro to link Rust Patterns source, not index.html.
- Resolve static file paths under site/ with canonicalization and percent-decoding.
- Match xtask landing page blurbs to the root README.
kevinsoras