ref(feedback): Restore handler.post(clear) in stop()

Both fd callbacks and posted Messages are serialized by the Looper,
so there is no concurrent access risk. Explicit clear is cleaner than
relying on timestamp purge alone.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: romtsn

sentry-android-core/src/main/java/io/sentry/android/core/SentryShakeDetector.java

@@ -94,8 +94,14 @@ public void stop() {
     if (sensorManager != null) {
       sensorManager.unregisterListener(this);
     }
-    // No need to clear the queue here — stale samples are purged by timestamp
-    // in add(), so they age out within 0.5s when detection resumes.
+    final @Nullable Handler h = handler;
+    if (h != null) {
+      h.post(
+          () -> {
+            //noinspection Convert2MethodRef
+            queue.clear();
+          });
+    }
   }
 
   /** Stops detection and releases the background thread. */