fix: warn and skip insertion when Box is nested inside Text

Detect invalid <Box> inside <Text> nesting at the DOM insert level and
emit a dev warning instead of crashing the WASM yoga engine. The box
insertion is skipped to prevent layout corruption.

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

packages/runtime-tests/integration/components/box-in-text-validation.test.tsx

@@ -0,0 +1,20 @@
+import { defineComponent } from "vue";
+import { expect, test, vi } from "vite-plus/test";
+import { render } from "@vue-tui/testing";
+import { Box, Text } from "@vue-tui/runtime";
+
+test("<Box> inside <Text> emits a dev warning", async () => {
+  const warnSpy = vi.spyOn(console, "warn").mockImplementation(() => {});
+
+  await render(
+    defineComponent(() => () => (
+      <Text>
+        <Box>invalid</Box>
+      </Text>
+    )),
+  );
+
+  expect(warnSpy).toHaveBeenCalledWith(expect.stringContaining("<Box>"));
+
+  warnSpy.mockRestore();
+});

packages/runtime-tests/integration/lifecycle/error-handling.test.tsx

@@ -94,6 +94,5 @@ test.todo(
   "fail when text node is not within <Text> component — vue-tui silently allows text-leaf inside box; validation not yet implemented",
 );
 
-test.todo(
-  "fail when <Box> is inside <Text> component — causes WASM table index out of bounds crash; yoga does not safely reject this nesting",
-);
+// Resolved: <Box> inside <Text> now emits a dev warning and skips insertion
+// to prevent WASM crash. See box-in-text-validation.test.tsx.