documents: inline formats toggle as Typora's

MarkdownDocument::format toggles bold, italic, code, strike, underline,
link and image at the selection, or clears every inline mark from the
blocks it touches, following Typora's toggleStyle: off inside the style,
wrap a selection, take the caret's word or write an empty pair. Code,
math, HTML and front matter refuse, as does a selection crossing a
block, a link or another mark. An open block keeps its field open.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/documents/mod.rs

@@ -36,8 +36,8 @@ pub use counts::{ReadingTime, WordCount};
 pub use diagram::{Diagram, diagram_svg};
 pub(crate) use diagram::{flatten, options as svg_options};
 pub use document::{
-    Attachment, DocumentEvent, DocumentHeading, DocumentLook, DocumentTarget, LARGEST_READ,
-    MarkdownDocument, TableEdit, TableRefusal, TargetBlock,
+    Attachment, DocumentEvent, DocumentHeading, DocumentLook, DocumentTarget, FormatRefusal,
+    InlineFormat, LARGEST_READ, MarkdownDocument, TableEdit, TableRefusal, TargetBlock,
 };
 pub use epub::{Chapter, EpubReader};
 pub use format::{Format, format};