feat(modify): commercial solutions keyword options for MOVE, COPY, FILLET, CHAMFER, OFFSET

MOVE: Displacement, Enter at the second point uses the base as the vector.
COPY: Displacement, mOde (Single/Multiple), Undo of the last copy.
FILLET: Undo of the last fillet (the command refreshes its entity cache
through the new CadCommand::on_document_undone hook after the host undoes
the document step). CHAMFER: Multiple and Undo. OFFSET: Erase (the offset
replaces its source), Layer (Current/Source), Undo, Exit.
POLY3D, TRACE, MIRROR and MEASUREGEOM expose the keywords they already
accepted as options, so the context menu and option buttons list them.

The pinned prompt now keeps informational bracket groups such as
"[3 objects]" and only drops real option listings when the buttons take over.

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

src/command.rs

@@ -2667,6 +2667,12 @@ pub trait CadCommand: Send {
     /// Default: no-op.
     fn inject_picked_entity(&mut self, _entity: acadrust::EntityType) {}
 
+    /// The host undid one document step on the command's behalf
+    /// (`CmdResult::UndoDocument`) and the command stays active. Commands
+    /// that cache document entities (FILLET, CHAMFER) refresh them here so
+    /// the next pick sees the restored geometry. Default: no-op.
+    fn on_document_undone(&mut self, _document: &acadrust::CadDocument) {}
+
     /// Supply the tessellated surface area associated with the picked entity.
     /// Commands that measure mesh-backed objects can opt in without owning the
     /// scene's render cache.