fix: resolve ruff lint violations

Break long function signature in delete_cluster_by_name to stay within
120-char line limit and remove unused json import from controller_test.

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

Author: raballew

python/packages/jumpstarter-kubernetes/jumpstarter_kubernetes/cluster/operations.py

@@ -51,7 +51,10 @@ def validate_cluster_type_selection(
 
 
 async def delete_cluster_by_name(  # noqa: C901
-    cluster_name: str, cluster_type: Optional[str] = None, force: bool = False, callback: Optional[OutputCallback] = None
+    cluster_name: str,
+    cluster_type: Optional[str] = None,
+    force: bool = False,
+    callback: Optional[OutputCallback] = None,
 ) -> None:
     """Delete a cluster by name, with auto-detection if type not specified."""
     if callback is None:

python/packages/jumpstarter-kubernetes/jumpstarter_kubernetes/controller_test.py

@@ -1,6 +1,5 @@
 """Tests for controller version resolution."""
 
-import json
 from unittest.mock import AsyncMock, patch
 
 import pytest