Components are frames (user bug #4)

What a component holds moves with its occurrence, and picks in the world land in the
component's frame:
- Sketches and construction planes show where their component is placed (free move, joint
  drive, Capture Position); sketch.inspect reports sketch points in the world.
- frames.rs maps a command's world picks into the frame of the body they lie on (through the
  inverse of its placement: a moved component or a pasted instance), points that make new
  geometry into the active component's frame, and directions with them; instance body names
  ("Body1 (Pin:2)") become the component's body. Fillet/chamfer edges, shell/offset/draft
  faces, face extrude/revolve, sketch on face, holes, sheet metal and plastic picks, primitives,
  appearance faces, analyses. Once per command (not again for commands run by commands); the
  active-frame fallback stays for commands without a table. Nothing changes while every
  placement is the identity.
- component.move_bodies keeps a body where it is in the world (Document.body_offsets: from the
  new component's frame to the one it was made in; renames and deleted components follow).
- The UI reads the placed model (Session::world_state) for display, picking, sketch editing and
  dialogs; live previews use it once anything is placed.
Tests (engine): sketches and construction planes move (and turn) with the component; world
picks fillet, sketch, hole and make boxes in a moved component; a pick on a pasted instance;
move_bodies keeps the world place there and back; a sketch on a face follows a Move feature.
QA's s34 now runs.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AS5Tn3xieewUSg3uxrMVdL

crates/ui-egui/src/dialogs_assembly_tests.rs

@@ -101,7 +101,10 @@ fn joint_and_drive_preview_on_the_placed_model() {
     assert_eq!(cmds[0].0, "FusionMoveJointsCommand");
     let b = world_preview(&app.session, &cmds, colors).unwrap().unwrap();
     assert_eq!(b.replaced, vec!["Body2".to_string()]);
-    assert!(world_preview(&app.session, &[("Extrude".into(), json!({}))], colors).is_none(), "features preview as before");
+    // Features preview as before while nothing is placed away from its frame, and on the
+    // placed model once something is (B moved by its joint).
+    assert!(world_preview(&two_boxes().session, &[("Extrude".into(), json!({}))], colors).is_none());
+    assert!(world_preview(&app.session, &[("Extrude".into(), json!({}))], colors).is_some());
 }
 
 /// Edit Joint changes type, alignment and limits of the joint in place.