pub fn render_syntax_reference() -> StringExpand description
Render the Syntax concept as a standalone reference document.
This is the single source for content/en/syntax.md (which is a committed,
drift-tested mirror) and for help syntax. Each Syntax fragment becomes a
## <title> section, in registry order. LANGUAGE.md stays hand-authored as
the deeper human reference; a test guards that it still covers this surface.