R6.7: ElyMark keeps a single line break on screen

Component 93efa7f draws soft breaks as lines (Typora's default when
writing); exports and copies read with MarkdownReader::joined, as GFM.

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

apps/ely-mark/src/output/html.rs

@@ -28,7 +28,7 @@ pub(super) fn write(
         placed,
         page,
         source,
-        reader: MarkdownReader::new(source, tree),
+        reader: MarkdownReader::joined(source, tree),
         anchored: HashSet::new(),
     };
     writer.root(tree)