Documents: open cells keep presses; finds open their cell

A press inside the open cell stays with its field. Find opens the
cell holding a match. A closing backslash no longer escapes the
next pipe. A right press after typed pipes reads the right byte.

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

src/documents/document/lists.rs

@@ -222,7 +222,7 @@ impl MarkdownDocument {
         true
     }
 
-    /// Tab or Shift-Tab in the open block; in a cell, the next or previous.
+    /// Tab or Shift-Tab; in a cell, moves between cells.
     pub(super) fn block_shift(
         &mut self,
         deeper: bool,