test: add case for direct cleanup on registration failure

src/ECharts.ts

@@ -351,7 +351,6 @@ export default defineComponent({
         // transition.
         root.value.__dispose = cleanup;
       } else {
-        /* c8 ignore next */
         cleanup();
       }
     });

tests/echarts-unregistered.test.ts

@@ -0,0 +1,48 @@
+import { describe, it, expect, beforeEach, vi } from "vitest";
+import { defineComponent, h, nextTick, shallowRef } from "vue";
+
+import { render } from "./helpers/testing";
+import { enqueueChart, resetECharts, type ChartStub } from "./helpers/mock";
+
+let chartStub: ChartStub;
+
+describe("ECharts component (wc unregistered)", () => {
+  beforeEach(() => {
+    resetECharts();
+    chartStub = enqueueChart();
+  });
+
+  it("calls cleanup directly when web component registration fails", async () => {
+    vi.resetModules();
+
+    vi.doMock("../src/wc", () => ({
+      TAG_NAME: "x-vue-echarts",
+      register: () => false,
+    }));
+
+    const { default: ECharts } = await import("../src/ECharts");
+
+    const exposed = shallowRef<any>();
+    const Root = defineComponent({
+      setup() {
+        return () =>
+          h(ECharts, {
+            option: { title: { text: "no-wc" } },
+            ref: (v: any) => (exposed.value = v),
+          });
+      },
+    });
+
+    const screen = render(Root);
+    await nextTick();
+
+    chartStub.dispose.mockClear();
+
+    screen.unmount();
+    await nextTick();
+
+    expect(chartStub.dispose).toHaveBeenCalledTimes(1);
+
+    vi.doUnmock("../src/wc");
+  });
+});