Strengthen is_connected with cached health probes.

Convert is_connected to a method that verifies backend liveness via TTL-cached ping (Redis) or bucket_exists (MinIO), with cache invalidation on connect/disconnect.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/integration/minio_adapter_test.py

@@ -115,7 +115,7 @@ def test_should_have_logger_when_instantiated() -> None:
 def test_should_not_be_connected_when_instantiated() -> None:
     """Test that the MinioAdapter is not connected when instantiated."""
     adapter = MinioAdapter()
-    assert not adapter.is_connected
+    assert not adapter.is_connected()
 
 
 def test_should_log_info_when_already_connected(
@@ -137,7 +137,7 @@ def test_should_raise_connection_error_when_unable_to_connect(
     adapter = MinioAdapter()
     with pytest.raises(ConnectionError):
         adapter.connect()
-    assert not adapter.is_connected
+    assert not adapter.is_connected()
 
 
 def test_should_log_info_when_creating_expected_bucket(
@@ -163,7 +163,7 @@ def test_should_log_error_on_exception_during_exit(
     """Test that the MinioAdapter logs an error if an exception occurs during __exit__."""
     try:
         with MinioAdapter() as adapter:
-            assert adapter.is_connected
+            assert adapter.is_connected()
             raise ValueError("Simulated error")
     except ValueError:
         pass  # Expected