fix: prevent deletion of library procedures

- Skip delete button creation for readonly blocks (data-readonly)
- Add WCProcedure.delete() override that guards against readonly

blocks-proc.js

@@ -25,6 +25,11 @@ const LIB_ICONS = {
 
 /** Procedure definition block with inputs/outputs/description/return-style. Lives in the Procedures tab. */
 class WCProcedure extends WCBlock {
+  delete() {
+    if (this.dataset.readonly) { showError("Cannot delete a library procedure."); return; }
+    super.delete();
+  }
+
   connectedCallback() {
     super.connectedCallback();
     this._el.naturalName = this._require(".proc-natural-name");