documents: lists go on, block lines shift, tables change, matches show, fences color by language

The document carries Markdown's editing tools for ElyMark (MARK-06):
Enter continues a list item or ends an empty one, Tab and Shift-Tab
shift an open block's lines, table rows and columns come and go as
one undo step, a match shows in any mode, replacements are one step,
and a fenced block colors by its language.

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

src/documents/mod.rs

@@ -34,7 +34,7 @@ pub use blocks::{Align, BlockData, BlockEditor, BlockEvent, BlockKind, Media};
 pub use contents::outline;
 pub use counts::{ReadingTime, WordCount};
 pub use diagram::Diagram;
-pub use document::{DocumentEvent, DocumentHeading, LARGEST_READ, MarkdownDocument};
+pub use document::{DocumentEvent, DocumentHeading, LARGEST_READ, MarkdownDocument, TableEdit};
 pub use epub::{Chapter, EpubReader};
 pub use format::{Format, format};
 pub(crate) use history::Change;