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.rs

@@ -240,7 +240,7 @@ fn pt(v: Vec3) -> Value {
 
 /// The occurrence placing a body (0: the root design), when the body is its primary instance.
 fn occurrence_of_body(s: &Session, body: &str) -> Option<u64> {
-    let st = s.model.state();
+    let st = s.world_state();
     let b = st.body(body)?;
     let comp = s.doc.body_component(&b.name, b.feature);
     if comp == 0 { Some(0) } else { s.doc.occurrence_of(comp).map(|o| o.id) }
@@ -769,7 +769,10 @@ fn next_joint_id(s: &Session) -> u64 {
 /// after is compared, so the components that move show where they go (`None`: not such
 /// commands).
 pub fn world_preview(s: &Session, cmds: &[(String, Value)], colors: Colors) -> Option<Result<Built, String>> {
-    if cmds.is_empty() || !cmds.iter().all(|(c, _)| MOVES.contains(&c.as_str())) {
+    // Any feature, when components are placed away from their frames: the preview must show
+    // the world the viewport shows.
+    let moves = cmds.iter().all(|(c, _)| MOVES.contains(&c.as_str()));
+    if cmds.is_empty() || !(moves || solvecraft_engine::frames::placed(s)) {
         return None;
     }
     let mut scratch = s.scratch();