refactor(audience): rename FlushAsync to FlushSync in EventQueue

Addresses cursor[bot] review comment on EventQueue.cs:67.

The method blocks synchronously and returns void — the Async suffix is
misleading in C# where it conventionally signals a Task-returning,
awaitable method. Renaming to FlushSync makes the blocking semantics
explicit.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ImmutableJeffrey

src/Packages/Audience/Runtime/Transport/EventQueue.cs

@@ -62,7 +62,7 @@ internal void Enqueue(string json)
         /// Drains the in-memory queue and persists all events to disk immediately.
         /// Blocks until the drain is complete.
         /// </summary>
-        internal void FlushAsync()
+        internal void FlushSync()
         {
             DrainMemoryToDisk();
         }

src/Packages/Audience/Tests/Runtime/EventQueueTests.cs

@@ -27,14 +27,14 @@ public void TearDown()
         }
 
         [Test]
-        public void Enqueue_ThenFlushAsync_PersistesEventToDisk()
+        public void Enqueue_ThenFlushSync_PersistesEventToDisk()
         {
             using var queue = new EventQueue(_store, flushIntervalSeconds: 60, flushSize: 100);
 
             queue.Enqueue("{\"event\":\"track\"}");
-            queue.FlushAsync();
+            queue.FlushSync();
 
-            Assert.AreEqual(1, _store.Count(), "event should be on disk after FlushAsync");
+            Assert.AreEqual(1, _store.Count(), "event should be on disk after FlushSync");
         }
 
         [Test]
@@ -45,7 +45,7 @@ public void Enqueue_MultipleEvents_AllPersistedAfterFlush()
             for (var i = 0; i < 10; i++)
                 queue.Enqueue($"{{\"i\":{i}}}");
 
-            queue.FlushAsync();
+            queue.FlushSync();
 
             Assert.AreEqual(10, _store.Count());
         }
@@ -65,7 +65,7 @@ public void FlushSize_Trigger_DrainsToDiskAutomatically()
                 Thread.Sleep(20);
 
             Assert.AreEqual(flushSize, _store.Count(),
-                "reaching FlushSize should trigger automatic drain without explicit FlushAsync");
+                "reaching FlushSize should trigger automatic drain without explicit FlushSync");
         }
 
         [Test]