MarkdownDocument: a Markdown file in one CodeEditor, shown visual, source, split or preview

Visual draws the top-level blocks in a gpui list; a pressed block opens as
its source and its typing is the text at once, written back as one undo
step. CodeEditor takes the owner's line colors, resets with a fresh
history and keeps at most 64 MiB of undo text. MarkdownMode gains Preview.

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

src/editor/line.rs

@@ -11,7 +11,6 @@ use super::{
     gutter::Cell,
     layout::{Shown, stack},
     state::{CodeEditor, CursorShape},
-    syntax,
 };
 use crate::{
     charts::tint,
@@ -29,7 +28,7 @@ impl CodeEditor {
         let touches = |span: &Range<usize>| {
             span.start < range.end.max(range.start + 1) && range.start < span.end
         };
-        let mut spans = syntax::colors(self.row_text(line), cx);
+        let mut spans = self.line_colors(self.row_text(line), cx);
         let brackets = self
             .frame
             .brackets