feat(grips): compatible grip shortcut menu

A right-click while a grip is hot opens the grip menu: Enter places the
grip, Stretch / Move / Rotate / Scale / Mirror switch how the gripped
objects are edited (the latter four hand the selection to the matching
command with the grip as its base point), Base Point re-bases the gesture
at the next click, Copy leaves the originals in place and adds the moved
shapes as new entities while keeping the grip hot, Undo snaps the shapes
back to where the gesture started, Exit drops the edit.

The grip commit path moves out of the left-release handler into
`commit_active_grip_edit` so the menu, Enter and the placement click share
it; Enter with a hot grip now places it instead of repeating the last
command.

Co-Authored-By: Claude Opus 5 <[email protected]>

src/app/command_driver.rs

@@ -176,6 +176,9 @@ impl OpenCADStudio {
 
     pub(super) fn cancel_active_grip_edit(&mut self) -> bool {
         let i = self.active_tab;
+        // Grip-menu toggles live only as long as the gesture.
+        self.tabs[i].grip_copy = false;
+        self.tabs[i].grip_base_pending = false;
         let had_grip = self.tabs[i].active_grip.take().is_some()
             || self.grip_add_provisional.is_some()
             || !self.grip_preview_handles.is_empty()