Components: occurrences with transforms (instances and Paste New copies), world placement of the model (Session::world_state for display, measure, export), active component authoring frame, move/ground/capture/revert positions, move bodies and sketches between components, rename/delete, migration of older designs

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

crates/engine/src/cmd/features.rs

@@ -236,6 +236,9 @@ fn check_expr(s: &Session, e: &str, kind: Kind, cmd: &str, what: &str) -> Result
 /// Add a feature, evaluate, and report its result (an evaluation error fails the command).
 fn add_feature(s: &mut Session, p: &Value, kind: FeatureKind) -> Result<Value> {
     let name = str_(p, "name");
+    // Commands speak world coordinates; the feature is authored in the active component.
+    let mut kind = kind;
+    super::component::to_active_frame(s, &mut kind);
     let id = s.doc_mut().add_feature(kind, name)?;
     let comp = s.active_component;
     if comp != 0