constraints: hide dynamic dimensions whose constraint did not load

A dynamic dimension is drawn by its constraint at screen size; without
the constraint it is a bare dimension with stretched extension lines.
Those orphans now stay undrawn and unplotted, as in a viewer (#992).

- First-release drawings keep dynamic dimensions on
  *LayerNameForDynamicConstraint; it counts as the dynamic layer.
- The hidden set is refreshed when constraints load, and the loader's
  prepared wires (built before that) are not installed while it holds
  anything.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/scene/mod.rs

@@ -3098,6 +3098,11 @@ impl Scene {
     /// so only immutable geometry is transferred and re-stamped here. The
     /// optional interaction index is cached against the exact same `Arc`.
     pub fn install_prepared_open_geometry(&self, prepared: PreparedOpenGeometry) {
+        // The loader tessellated before the constraints were read, so its
+        // wires still hold the dynamic dimensions that must stay hidden.
+        if !self.hidden_dynamic_dimensions.is_empty() {
+            return;
+        }
         let block = self.model_space_block_handle();
         let scale = crate::scene::annotative::scale_handle_by_name(
             &self.document,