test(tsconnect): bound cancel timeout control

Co-Authored-By: gpt-5.6-sol <noreply@openai.com>

cmd/tsconnect/wasm/bridge_test.go

@@ -185,8 +185,16 @@ func TestJSStreamReaderCloseErrors(t *testing.T) {
 }
 
 func TestJSStreamReaderCloseTimesOut(t *testing.T) {
+	deferred := evalJS(t, `(() => {
+		let timer
+		return {
+			reader: {cancel() { return {then(resolve) { timer = setTimeout(resolve, 200) }} }},
+			stop() { clearTimeout(timer) },
+		}
+	})()`)
+	defer deferred.Call("stop")
 	r := &jsStreamReader{
-		reader:            evalJS(t, `({cancel() { return new Promise(() => {}) }})`),
+		reader:            deferred.Get("reader"),
 		testCancelTimeout: 10 * time.Millisecond,
 	}
 	started := time.Now()