Command line: the bare-word probe keeps no empty undo step

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/app/command_driver/utilities.rs

@@ -798,9 +798,14 @@ impl OpenCADStudio {
         {
             return self.dispatch_command(cmd);
         }
+        // Close an earlier step first so only what the probe opens is dropped below.
+        self.finish_pending_history(i);
         let start_task = self.dispatch_command(tokens[0]);
         if self.tabs[i].active_cmd.is_none() {
             // Not an interactive tool — an inline-argument command (`PDMODE 3`).
+            // The bare word only probed it: a step it kept without changing
+            // anything is not an undo step of its own.
+            self.drop_unchanged_pending_history(i);
             return self.dispatch_command(cmd);
         }
         let toks: Vec<String> = tokens.iter().map(|s| s.to_string()).collect();

src/app/history.rs

@@ -341,6 +341,15 @@ impl OpenCADStudio {
         self.push_undo_entry(i, HistorySnapshot::Delta(Box::new(delta)));
     }
 
+    /// Finish the pending history step, dropping it when it changed nothing
+    /// even if it was opened as a mark ([`Self::push_undo_mark`]).
+    pub(super) fn drop_unchanged_pending_history(&mut self, i: usize) {
+        if let Some(pending) = self.tabs[i].history.pending.as_mut() {
+            pending.keep_empty = false;
+        }
+        self.finish_pending_history(i);
+    }
+
     pub(super) fn finish_all_pending_history(&mut self) {
         for i in 0..self.tabs.len() {
             self.finish_pending_history(i);