add pumpAsync test helper — bounded settle for async widget tests

A reusable helper in the shared harness that drains microtasks + advances
one short fake-time tick, replacing the two patterns that have repeatedly
wedged the suite (and the pre-push gate) for ~10 minutes each: pumpAndSettle
(loops until quiescent — hangs on perpetual animation / overlapping async)
and `await Future.delayed(Duration.zero)` inside testWidgets (a real timer
that never fires under fake-async). Bounded by construction — cannot hang.

Co-Authored-By: Claude <noreply@anthropic.com>

test/helpers/widget_harness.dart

@@ -1,5 +1,6 @@
 import 'package:clide/kernel/kernel.dart';
 import 'package:flutter/widgets.dart';
+import 'package:flutter_test/flutter_test.dart';
 
 import 'kernel_fixture.dart';
 
@@ -33,3 +34,23 @@ Widget harness(KernelFixture fixture, Widget child) {
     ),
   );
 }
+
+/// Settle async-driven UI in a widget test WITHOUT the two patterns that have
+/// repeatedly wedged this suite:
+///
+/// - **Never `pumpAndSettle()`** — it loops until the frame queue is quiescent,
+///   so a perpetual animation or overlapping async loads hang it for its
+///   ~10-minute default timeout (which wedged the pre-push gate).
+/// - **Never `await Future.delayed(Duration.zero)`** — inside the fake-async
+///   `testWidgets` zone a real timer never fires unless fake time is advanced,
+///   so that line wedges the test until timeout (and even defeats `--timeout`).
+///
+/// Instead: pump one frame (draining the microtask queue — broadcast-stream and
+/// async-IPC deliveries resolve here), then advance a tiny fake-time tick to
+/// flush any follow-up `setState`. Bounded by construction — it cannot hang.
+/// Use this after publishing a message / triggering a load in a reader/panel
+/// widget test, in place of `pumpAndSettle`.
+Future<void> pumpAsync(WidgetTester tester) async {
+  await tester.pump();
+  await tester.pump(const Duration(milliseconds: 20));
+}