Wire up the Properties panel's Parameters section

PropValue::ParamRow/ParamAddRow, the PropParamInput/Commit/Delete/AddNew
messages, their command_driver handlers (on_prop_param_commit/_delete/
_add_new, resolve_named_parameter_edit), and their render functions all
already existed — but nothing ever constructed the "Parameters" section
that would route data to them, so the whole inline add/rename/redefine/
delete workflow was unreachable from the UI. Adds that missing section
to the no-selection page in refresh_properties, alongside a new
PropValue::ParamsVisibilityToggle header row (mirrors the existing
show_constraint_values setting) for toggling whether constraint pills
show their driven value/parameter name.

Users can now manage named parameters inline in the Properties panel
(live resolved values, add/rename/redefine/delete) as an alternative to
the separate PARAMETERS modal, which continues to work unchanged.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

src/scene/model/object.rs

@@ -80,6 +80,11 @@ pub enum PropValue {
     },
     /// The trailing "+ Add parameter" row in the Parameters section.
     ParamAddRow,
+    /// The Parameters section's leading header row (no-selection page only):
+    /// a global on/off toggle for whether any constraint pill in the
+    /// viewport shows its driven value/parameter-name text. Mirrors
+    /// `App::show_constraint_values`.
+    ParamsVisibilityToggle(bool),
 }
 
 /// A single property row in the Properties panel.