fix(ai): forwarded advisor silence flag over pi-native

Added acceptEmptyResponse to the pi-native gateway option allow-list so a Google advisor on the auth-gateway transport still accepts a silent STOP server-side instead of exhausting the empty-response retries.

Added a pi-native parseRequest regression asserting the option survives the wire.

packages/ai/src/providers/pi-native-server.ts

@@ -78,6 +78,7 @@ const ALLOWED_OPTION_KEYS: ReadonlySet<keyof SimpleStreamOptions> = new Set([
 	"preferWebsockets",
 	"openrouterVariant",
 	"loopGuard",
+	"acceptEmptyResponse",
 ] as const satisfies readonly (keyof SimpleStreamOptions)[]);
 
 // ---------------------------------------------------------------------------

packages/ai/test/auth-gateway-pi-native.test.ts

@@ -145,6 +145,15 @@ describe("pi-native parseRequest", () => {
 		expect(parsed.options.loopGuard).toEqual({ enabled: false });
 	});
 
+	it("forwards acceptEmptyResponse so a passive Google advisor can accept silence server-side", () => {
+		const parsed = parseRequest({
+			modelId: "google/gemini-3.6-flash",
+			context: baseContext,
+			options: { acceptEmptyResponse: true },
+		});
+		expect(parsed.options.acceptEmptyResponse).toBe(true);
+	});
+
 	it("forwards an explicit statefulResponses disablement to the native stream", () => {
 		const parsed = parseRequest({
 			modelId: "openai/gpt-5",