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/entities/dimension.rs

@@ -7860,10 +7860,7 @@ fn radial_leader_tip(dim: &Dimension, text: Vector3) -> Vector3 {
 /// A dimensional constraint's dynamic dimension: the reference keeps it on
 /// its own hidden layer and draws it by its own rules.
 fn dynamic_constraint_dimension(dim: &Dimension) -> bool {
-    dim.base()
-        .common
-        .layer
-        .eq_ignore_ascii_case(crate::scene::parametric_constraints::DYNAMIC_DIMENSION_LAYER)
+    crate::scene::parametric_constraints::is_dynamic_dimension_layer(&dim.base().common.layer)
 }
 
 /// How far a radial leader runs out from the rim before its hook, and how