fix: move probe healthy log to req.onsuccess to avoid false positive

The "connection is healthy" log was emitted synchronously after
count(), before the IDB request completed. If the request later
failed via onerror, both healthy and stale logs would fire for
the same visibility event. Now only logs on actual success.

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

Author: leshniak

lib/storage/providers/IDBKeyValProvider/createStore.ts

@@ -164,10 +164,12 @@ function createStore(dbName: string, storeName: string): UseStore {
                     const tx = db.transaction(storeName, 'readonly');
                     const probeStore = tx.objectStore(storeName);
                     const req = probeStore.count();
+                    req.onsuccess = () => {
+                        Logger.logInfo('IDB visibilitychange probe: connection is healthy', {dbName, storeName});
+                    };
                     req.onerror = () => {
                         dropCacheIfStale(req.error);
                     };
-                    Logger.logInfo('IDB visibilitychange probe: connection is healthy', {dbName, storeName});
                 } catch (error) {
                     dropCacheIfStale(error);
                 }