documents: dropped files and pasted pictures go to the owner; insert puts text at the caret

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

src/documents/mod.rs

@@ -35,7 +35,8 @@ pub use contents::outline;
 pub use counts::{ReadingTime, WordCount};
 pub use diagram::Diagram;
 pub use document::{
-    DocumentEvent, DocumentHeading, LARGEST_READ, MarkdownDocument, TableEdit, TableRefusal,
+    Attachment, DocumentEvent, DocumentHeading, LARGEST_READ, MarkdownDocument, TableEdit,
+    TableRefusal,
 };
 pub use epub::{Chapter, EpubReader};
 pub use format::{Format, format};