W66: Editor Delete command in Edit menu (MC CK_Remove)

Add Delete EditorCmd variant and wire it into the F9 Edit menu
between Paste and Select All. With a selection, deletes the
selected text. Without a selection, deletes one character
forward (select_right + delete_selection).

Added 1 unit test verifying single-character forward delete.

Tests: 1425 pass (was 1424), zero warnings.

local/recipes/tui/tlc/source/src/editor/menubar.rs

@@ -91,6 +91,8 @@ pub enum EditorCmd {
     Close,
     /// Toggle insert/overwrite mode (INS key, MC CK_InsertOverwrite).
     ToggleOverwrite,
+    /// Delete character/selection (MC CK_Remove).
+    Delete,
 }
 
 /// Outcome of a menu-bar key press.
@@ -215,6 +217,7 @@ impl EditorMenuBar {
                     MenuItem::item("Cut", 'x', EditorCmd::Cut),
                     MenuItem::item("Copy", 'c', EditorCmd::Copy),
                     MenuItem::item("Paste", 'v', EditorCmd::Paste),
+                    MenuItem::item("Delete", 'd', EditorCmd::Delete),
                     MenuItem::separator(),
                     MenuItem::item("Select all", 'a', EditorCmd::MarkAll),
                 ],

local/recipes/tui/tlc/source/src/editor/mod.rs

@@ -1310,6 +1310,23 @@ impl Editor {
                     self.message = Some("Block copied".to_string());
                 }
             }
+            EditorCmd::Delete => {
+                if self.cursor.has_selection() {
+                    self.cursor.delete_selection(&mut self.buffer);
+                    self.cursor.set_position(self.buffer.cursor(), &self.buffer);
+                    self.modified = self.buffer.is_modified();
+                    self.message = Some("Deleted".to_string());
+                } else {
+                    // Delete forward one character.
+                    self.cursor.set_position(self.buffer.cursor(), &self.buffer);
+                    let _ = self.cursor.select_right(&mut self.buffer);
+                    if self.cursor.has_selection() {
+                        self.cursor.delete_selection(&mut self.buffer);
+                        self.cursor.set_position(self.buffer.cursor(), &self.buffer);
+                        self.modified = self.buffer.is_modified();
+                    }
+                }
+            }
             EditorCmd::Paste => {
                 if let Some(text) = self.clipboard.clone() {
                     if self.cursor.has_selection() {
@@ -3922,6 +3939,17 @@ mod tests {
         assert!(e.mode.is_prompt());
     }
 
+    #[test]
+    fn delete_forward_without_selection_removes_one_char() {
+        let mut e = make_empty();
+        e.insert_str("ab");
+        e.buffer.set_cursor(0);
+        e.cursor.set_position(0, &e.buffer);
+        let _ = e.dispatch_editor_cmd(crate::editor::menubar::EditorCmd::Delete);
+        assert_eq!(e.buffer.len(), 1);
+        assert_eq!(e.buffer.as_string(), "b");
+    }
+
     #[test]
     fn toggle_overwrite_cycles_ovr_ins() {
         let mut e = make_empty();