refactor: address Sonar warnings in label helpers

Author: stephenlclarke

test/ScopeTimerTest.cpp

@@ -40,6 +40,7 @@ class ScopeTimer_TestFriend {
         test_labelarg_literal_and_pointer_variants();
         test_labeldata_manual_empty_view();
         test_labelarg_empty_literal_to_labeldata();
+        test_labeldata_constructor_default_view();
         test_labelarg_owned_to_labeldata();
         test_scope_timer_string_view_ctor();
         test_looped_work();
@@ -263,6 +264,12 @@ class ScopeTimer_TestFriend {
         expect(data.storage.empty(), "LabelArg empty literal does not allocate storage");
     }
 
+    static void test_labeldata_constructor_default_view() {
+        ::xyzzy::scopetimer::detail::LabelData data(std::string_view{});
+        expect(data.view == std::string_view("ScopeTimer"), "LabelData ctor defaults empty inputs to ScopeTimer");
+        expect(data.storage.empty(), "LabelData ctor leaves storage empty when no ownership provided");
+    }
+
     static void test_labelarg_owned_to_labeldata() {
         std::string ownedSource = "tests:label:owned";
         ::xyzzy::scopetimer::detail::LabelArg arg{std::move(ownedSource)};