fix(tui): keep panel and line-open state consistent

Clamp panel scroll when row updates shrink the visible model so panel rendering cannot skip past the remaining rows.

Keep direct line-open insert actions in the active insert transaction so typing after `InsertLineBelowCursor` or `InsertLineAtCursor` undoes as one insert session.

Author: fcoury

src/editor.rs

@@ -2641,9 +2641,6 @@ impl Editor {
                 self.cy += 1;
                 self.cx = leading_spaces;
                 self.mode = Mode::Insert;
-                if started_transaction {
-                    self.commit_transaction(self.cursor_snapshot());
-                }
 
                 if self.cy >= self.vheight() {
                     self.vtop += 1;
@@ -2676,9 +2673,6 @@ impl Editor {
                 self.notify_change(runtime).await?;
                 self.cx = leading_spaces;
                 self.mode = Mode::Insert;
-                if started_transaction {
-                    self.commit_transaction(self.cursor_snapshot());
-                }
                 self.render(buffer)?;
             }
             Action::MoveToTop => {

src/plugin/panel.rs

@@ -93,6 +93,10 @@ impl PluginPanel {
         } else if self.selected >= self.rows.len() {
             self.selected = self.rows.len() - 1;
         }
+
+        if self.scroll > self.selected {
+            self.scroll = self.selected;
+        }
     }
 
     pub fn move_selection(&mut self, delta: isize, height: usize) {
@@ -324,4 +328,17 @@ mod tests {
         assert_eq!(event.selected_index, 1);
         assert_eq!(event.row.unwrap().id, "b");
     }
+
+    #[test]
+    fn update_rows_clamps_scroll_to_remaining_rows() {
+        let mut panel = PluginPanel::new("tree".to_string(), PanelConfig::default());
+        panel.update_rows((0..10).map(|i| row(&i.to_string())).collect());
+        panel.selected = 8;
+        panel.scroll = 6;
+
+        panel.update_rows(vec![row("a"), row("b")]);
+
+        assert_eq!(panel.selected, 1);
+        assert_eq!(panel.scroll, 1);
+    }
 }

tests/editing.rs

@@ -855,6 +855,25 @@ async fn test_yank_and_paste() {
     // This depends on clipboard/register implementation
 }
 
+#[tokio::test]
+async fn test_direct_open_line_below_groups_insert_undo() {
+    let mut harness = EditorHarness::with_content("Line 1\nLine 2");
+
+    harness
+        .execute_action(Action::InsertLineBelowCursor)
+        .await
+        .unwrap();
+    harness.type_text("New line").await.unwrap();
+    harness
+        .execute_action(Action::EnterMode(Mode::Normal))
+        .await
+        .unwrap();
+
+    harness.assert_buffer_contents("Line 1\nNew line\nLine 2");
+    harness.execute_action(Action::Undo).await.unwrap();
+    harness.assert_buffer_contents("Line 1\nLine 2");
+}
+
 #[tokio::test]
 async fn test_editing_empty_buffer() {
     let mut harness = EditorHarness::new();