feat(runtime-tests): integration test suite

21 test files covering components, composables, focus, lifecycle,
and scheduler through the public render() API.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/runtime-tests/integration/components/text.test.tsx

@@ -0,0 +1,20 @@
+import { expect, test } from "vite-plus/test";
+import { render } from "@vue-tui/testing";
+import { Text } from "@vue-tui/runtime";
+
+test("nested Text renders inline without independent layout", async () => {
+  const { lastFrame } = await render(() => (
+    <Text>
+      Hello <Text color="red">world</Text>
+    </Text>
+  ));
+  const frame = lastFrame()!;
+  expect(frame).toContain("Hello");
+  expect(frame).toContain("world");
+});
+
+test("CJK wide characters render without corruption", async () => {
+  const { lastFrame } = await render(() => <Text>中文测试</Text>, { columns: 20 });
+  const frame = lastFrame()!;
+  expect(frame).toContain("中文测试");
+});