fix(tui): let command-backspace delete preceding newlines

src/tui/app.rs

@@ -6375,6 +6375,22 @@ mod tests {
         assert!(app.attachments.is_empty());
     }
 
+    #[test]
+    fn line_start_deletion_keys_continue_through_newlines() {
+        for key in [
+            modified_press(KeyCode::Backspace, KeyModifiers::SUPER),
+            modified_press(KeyCode::Char('u'), KeyModifiers::CONTROL),
+        ] {
+            let mut app = app();
+            app.paste("first\nsecond");
+            for expected in ["first\n", "first", "", ""] {
+                app.handle_key(key);
+                assert_eq!(app.editor.text(), expected);
+                assert_eq!(app.editor.cursor(), expected.len());
+            }
+        }
+    }
+
     #[test]
     fn attachment_placeholder_includes_a_separator_before_following_text() {
         let mut app = app();

src/tui/editor.rs

@@ -236,9 +236,14 @@ impl Editor {
         self.text.replace_range(self.cursor..target, "");
     }
 
-    /// `ctrl+u` / `cmd+backspace`: erase from the cursor to the line start.
+    /// `ctrl+u` / `cmd+backspace`: erase from the cursor to the line start,
+    /// or erase the preceding newline when already at the line start.
     pub fn delete_to_line_start(&mut self) {
         let (start, _) = self.line_bounds(self.cursor);
+        if start == self.cursor {
+            self.backspace();
+            return;
+        }
         self.text.replace_range(start..self.cursor, "");
         self.cursor = start;
     }
@@ -447,6 +452,28 @@ mod tests {
         assert_eq!(editor.text(), "first\n");
     }
 
+    #[test]
+    fn deleting_to_line_start_can_continue_through_previous_lines() {
+        let mut editor = editor("café\n\nsecond");
+        for expected in ["café\n\n", "café\n", "café", "", ""] {
+            editor.delete_to_line_start();
+            assert_eq!(editor.text(), expected);
+            assert_eq!(editor.cursor(), expected.len());
+        }
+    }
+
+    #[test]
+    fn deleting_at_line_start_preserves_text_after_the_cursor() {
+        let mut editor = editor("café\nsecond");
+        editor.move_line_start();
+        editor.delete_to_line_start();
+        assert_eq!(editor.text(), "cafésecond");
+        assert_eq!(editor.cursor(), "café".len());
+        editor.delete_to_line_start();
+        assert_eq!(editor.text(), "second");
+        assert_eq!(editor.cursor(), 0);
+    }
+
     #[test]
     fn keeps_the_column_when_moving_between_lines() {
         let mut editor = editor("abcdef\nxy\nlonger");