fix(test): drop eager connectivity listener in MutationReplayer

ref.listen(connectivityProvider, …) at start-time mounted the
StreamProvider immediately, which kicked off checkConnectivity()
with a 2s timeout. In tests that never reach the auth state
(smoke_test cold-launch path), that Timer leaked past widget tree
dispose and tripped the still-pending-timer assertion.

Drop the edge trigger — the 3s initial + 1min periodic + post-
enqueue nudge already cover the drain paths. Worst case on
reconnect is ~60s extra latency before the queue drains, which
is acceptable for an offline-resilience layer.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

flutter_client/lib/cache/mutation_queue.dart

@@ -38,7 +38,6 @@ import '../playlists/playlists_provider.dart' show playlistsApiProvider;
 import '../quarantine/quarantine_provider.dart' show quarantineApiProvider;
 import '../requests/requests_provider.dart' show requestsApiProvider;
 import 'audio_cache_manager.dart' show appDbProvider;
-import 'connectivity_provider.dart';
 import 'db.dart';
 
 /// Stable kind constants. Each controller emits one of these via
@@ -111,16 +110,12 @@ class MutationReplayer {
     // from a prior session that died offline. 3s lets the auth +
     // server-url + dio providers finish their async warmup.
     _initialTimer = Timer(const Duration(seconds: 3), drain);
-
-    // Drain on every connectivity emission that resolves to online.
-    // ref.listen fires on changes after subscription; we don't get
-    // the initial value, but the Timer above + the periodic poll
-    // cover that.
-    _ref.listen(connectivityProvider, (prev, next) {
-      final isOnline = next.value ?? false;
-      if (isOnline) unawaited(drain());
-    });
-
+    // Periodic ticker is the only reconnect signal. We previously had
+    // a ref.listen(connectivityProvider, …) edge trigger here, but
+    // subscribing at start-time eagerly mounted the connectivity
+    // StreamProvider and leaked its initial-timeout Timer through
+    // tests that never reach the auth state. The drain() loop itself
+    // gates on connectivity via the .future read below.
     _intervalTimer = Timer.periodic(_interval, (_) => drain());
   }