test(kanban): exercise checked form handler path

Add a kanban example smoke test for #[slhx::form] plus #[slhx::handler] over the generated create_card form resource.

req: form/001

req: form/004

req: form/006

req: derive_handler/003

examples/kanban/src/lib.rs

@@ -15,6 +15,14 @@ mod tests {
         columns: Vec<String>,
     }
 
+    #[allow(dead_code)]
+    #[derive(Clone, Debug)]
+    #[slhx::form("create_card")]
+    struct CreateCard {
+        title: String,
+        column: String,
+    }
+
     // req: examples/001 req: codegen/002 req: list/003
     #[test]
     fn kanban_board_updates_generated_slot() {
@@ -48,6 +56,20 @@ mod tests {
         Selector::parse(value).expect("test selector parses")
     }
 
+    // req: examples/001 req: form/001 req: form/004 req: form/006 req: derive_handler/003
+    #[test]
+    fn kanban_form_handler_is_checked_against_hemplate_form() {
+        #[slhx::handler]
+        fn create_card(_form: slhx::Form<CreateCard>) -> impl IntoEffect {
+            ui::board::slots::notice.text("queued")
+        }
+
+        let effect = inspect(create_card(ui::board::forms::create_card.typed::<CreateCard>()));
+
+        assert!(effect.has_slot(ui::board::slots::notice));
+        assert!(matches!(effect.ops(), [Effect::Put { payload: Payload::Text(_), .. }]));
+    }
+
     // req: examples/001 req: form/002 req: codegen/003
     #[test]
     fn kanban_template_exports_form_and_card_handles() {