documents: a dropped block hands its focus to the document

An edit past an open block wrote it back and dropped its input while
it held focus, so focus fell to the window root and Undo reached
nothing. The next render passes such focus to the document.

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

src/documents/document/tests/tools.rs

@@ -411,3 +411,24 @@ fn delete_table_takes_the_table_or_refuses_outside(cx: &mut TestAppContext) {
     assert_eq!(*heard.borrow(), [outside]);
     assert_eq!(text(&document, cx), source);
 }
+
+#[gpui::test]
+fn undo_follows_a_table_edit_that_closes_the_block(cx: &mut TestAppContext) {
+    let source = "before\n\n| A |\n| - |\n| 1 |\n\nafter\n";
+    let (document, cx) = open(source, MarkdownMode::Visual, cx);
+    press(1, Modifiers::none(), cx);
+    document.update(cx, |document, cx| {
+        document
+            .edit_table(crate::documents::TableEdit::Delete, cx)
+            .expect("taken")
+    });
+    cx.run_until_parked();
+    assert_eq!(text(&document, cx), "before\n\nafter\n");
+    let held = cx.update(|window, cx| {
+        let handle = gpui::Focusable::focus_handle(document.read(cx), cx);
+        handle.contains_focused(window, cx)
+    });
+    assert!(held, "focus stays in the document");
+    cx.simulate_keystrokes("secondary-z");
+    assert_eq!(text(&document, cx), source);
+}