feat(layout): add TerminalTestcaseLayout component for rendering testcase content

src/app/(app)/problems/[id]/@terminal/@testcase/layout.tsx

@@ -0,0 +1,13 @@
+interface TerminalTestcaseLayoutProps {
+  children: React.ReactNode;
+}
+
+export default function TerminalTestcaseLayout({
+  children,
+}: TerminalTestcaseLayoutProps) {
+  return (
+    <div className="h-full flex flex-col">
+      <div className="flex-1">{children}</div>
+    </div>
+  );
+}