feat(blocks): wire Stretch actions and independent reference evaluation

Author a native Stretch action from a Linear, Polar or XY parameter, a two-corner stretch frame, an object selection and a marker. Preview and retain its frame in BEDIT, with selectable and movable action markers.

Freeze line and planar lightweight-polyline vertex bindings, preserve curved-segment height, move wholly selected objects, and evaluate independent saved INSERTs from their definition. Retain native DWG/DXF data, copied-reference isolation and undo/redo.

Validate with synthetic frame, topology, parameter, history, Test Block, drawing-reference, COPY and roundtrip regressions: 340 block tests pass (6 existing opt-in ignored), plus 41 dock and 27 viewport tests. Other entity types, Polar Stretch, custom multipliers and chaining remain unsupported.

src/app/view/mod.rs

@@ -1203,8 +1203,19 @@ bg={bg_ms:.1}ms n={view_count}"
                             session.br_handle,
                         )
                         .into_iter()
-                        .map(|(_, action, _, _)| {
+                        .map(|(handle, action, _, _)| {
                             let mut g = crate::scene::block_distance_parameter::Graphic::default();
+                            let frame = crate::scene::block_actions::frame_outline(
+                                &tab.scene.document,
+                                handle,
+                            );
+                            g.lines.extend(
+                                frame
+                                    .iter()
+                                    .zip(frame.iter().cycle().skip(1))
+                                    .take(frame.len())
+                                    .map(|(a, b)| [*a, *b]),
+                            );
                             g.grips.push((action.display_location, false));
                             g.labels
                                 .push((action.display_location, action.element.name.clone()));