feat: add form and page platform

tests/fixtures/architecture/forbidden/template-imports-application.tsx

@@ -0,0 +1,5 @@
+import type { ApplicationApi } from "../../../../src/application/ports/in/application-api.js";
+
+export function ForbiddenTemplate(_props: { application: ApplicationApi }) {
+  return <main>Template must not select an application use case.</main>;
+}

tests/fixtures/typecheck/invalid-page-action.tsx

@@ -0,0 +1,6 @@
+import type { PageActionDefinition } from "../../../src/presentation/templates/index.js";
+
+export const activeButtonWithoutCallback = {
+  kind: "button",
+  label: "Unsafe active action",
+} satisfies PageActionDefinition;