Themed HTML export

Standalone HTML export that tracks the editor theme, optional prefers-color-scheme (Auto), accent-aware CSS, fenced-code highlighting via syntect through comrak, and flowchart Mermaid as inline SVG.

User-facing behavior

• Dialog: Settings are persisted in Settings.html_export_options (src/export/html_options.rs). UI: render_html_export_dialog in src/app/dialogs.rs, toggled by UiState.show_html_export_dialog (shortcut opens the dialog; export runs from there).
• Self-contained vs linked: Controlled by HtmlExportOptions.self_contained, ImageHandling, and post-processing in src/export/html.rs.
• Clipboard: Copy as HTML continues to use the fragment/clipboard path in src/export/clipboard.rs (unchanged contract).

Implementation map

Concern	Location
Full document assembly	generate_html_document_export, generate_html_document (src/export/html.rs)
Theme resolution (single / auto light+dark)	HtmlThemeResolution, resolve_html_theme_for_export, theme_rules_inner (html.rs)
Syntax highlighting in fences	FerriteHtmlHighlighter — SyntaxHighlighterAdapter, syntect append_highlighted_html_for_styled_line into a String then write (html.rs)
Mermaid	extract_mermaid_fences, inject_mermaid_exports; flowchart SVG try_flowchart_svg_snippet (src/export/flowchart_svg.rs)
Flowchart types for SVG	Re-exported from src/markdown/mermaid/mod.rs; diagram kind detect_mermaid_diagram_type from src/markdown/mod.rs
Images / relative links	postprocess_images, postprocess_links (html.rs); shared enums in src/export/options.rs
PDF sibling (theme colors)	PdfTheme::from_theme_colors — see pdf-export.md

Related

• End-user and clipboard overview: document-export.md