fix: register google vertex setup provider

extensions/google/setup-api.test.ts

@@ -0,0 +1,21 @@
+import { describe, expect, it } from "vitest";
+import setupEntry from "./setup-api.js";
+
+describe("google setup entry", () => {
+  it("registers setup runtime providers declared by the manifest", () => {
+    const providerIds: string[] = [];
+    const cliBackendIds: string[] = [];
+
+    setupEntry.register({
+      registerProvider(provider) {
+        providerIds.push(provider.id);
+      },
+      registerCliBackend(backend) {
+        cliBackendIds.push(backend.id);
+      },
+    } as never);
+
+    expect(providerIds).toContain("google-vertex");
+    expect(cliBackendIds).toContain("google-gemini-cli");
+  });
+});