test(cli): cover static Switchyard migration validation

Signed-off-by: Bryan Bednarski <bbednarski@nvidia.com>

Author: bbednarski9

crates/cli/tests/coverage/shared/server_tests.rs

@@ -1837,6 +1837,28 @@ async fn static_only_cli_configuration_keeps_the_legacy_lifecycle() {
     let _ = deregister_plugin(GENERIC_TEST_PLUGIN_KIND);
 }
 
+#[test]
+fn register_and_validate_plugin_components_rejects_legacy_switchyard_components() {
+    for enabled in [true, false] {
+        let config = PluginConfig {
+            components: vec![PluginComponentSpec {
+                kind: "switchyard".into(),
+                enabled,
+                config: Map::new(),
+            }],
+            ..PluginConfig::default()
+        };
+
+        let errors = register_and_validate_plugin_components(&config);
+        assert!(
+            errors
+                .iter()
+                .any(|error| matches!(error, PluginComponentSetupError::RemovedSwitchyard)),
+            "legacy Switchyard components must be rejected when enabled is {enabled}"
+        );
+    }
+}
+
 #[test]
 fn plugin_component_setup_errors_render_every_diagnostic_variant() {
     let adaptive = PluginComponentSetupError::Adaptive("adaptive failure".into());