[NOGIL] Split schema_registry tests to narrow free-threaded test exclusions (#2309)

* [NOGIL] Split schema_registry tests to narrow free-threaded test exclusions

  Each of test_avro_serdes.py, test_config.py, test_json_serdes.py, and
  test_proto_serdes.py is split into a plain file (no rules/encryption
  dependency) and a _rules file (CEL/encryption/JSONata-dependent tests).
  This lets the plain tests run on free-threaded (3.14t) builds, where
  tink/celpy/orjson have no free-threaded wheels, while only the _rules
  files stay excluded via conftest.py's collect_ignore.

* Fix isort/black formatting in split schema_registry tests

Author: ojasvajain

tests/schema_registry/_async/test_avro_serdes.py

@@ -23,8 +23,6 @@
 
 from confluent_kafka.schema_registry import AsyncSchemaRegistryClient
 from confluent_kafka.schema_registry.common.schema_registry_client import normalize_identity_pool
-from confluent_kafka.schema_registry.rules.encryption.encrypt_executor import FieldEncryptionExecutor
-from confluent_kafka.schema_registry.serde import RuleError
 
 TEST_URL = 'http://SchemaRegistry:65534'
 TEST_USERNAME = 'sr_user'
@@ -402,30 +400,6 @@ def test_config_unknown_prop():
         AsyncSchemaRegistryClient(conf)
 
 
-def test_config_encrypt_executor():
-    executor = FieldEncryptionExecutor()
-    client_conf = {'url': 'mock://'}
-    rule_conf = {'key': 'value'}
-    executor.configure(client_conf, rule_conf)
-    # configure with same args is fine
-    executor.configure(client_conf, rule_conf)
-    rule_conf2 = {'key2': 'value2'}
-    # configure with additional rule_conf keys is fine
-    executor.configure(client_conf, rule_conf2)
-
-    client_conf2 = {
-        'url': 'mock://',
-        'ssl.key.location': '/ssl/keys/client',
-        'ssl.certificate.location': '/ssl/certs/client',
-    }
-    with pytest.raises(RuleError, match="executor already configured"):
-        executor.configure(client_conf2, rule_conf)
-
-    rule_conf3 = {'key': 'value3'}
-    with pytest.raises(RuleError, match="rule config key already set: key"):
-        executor.configure(client_conf, rule_conf3)
-
-
 def test_normalize_identity_pool_none():
     assert normalize_identity_pool(None) is None
 

tests/schema_registry/_async/test_avro_serdes_rules.py

@@ -0,0 +1,51 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+#
+# Copyright 2026 Confluent Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+import pytest
+
+from confluent_kafka.schema_registry.rules.encryption.encrypt_executor import FieldEncryptionExecutor
+from confluent_kafka.schema_registry.serde import RuleError
+
+"""
+Tests for config handling that depend on the rules extra (tink/celpy) and
+are excluded from collection on free-threaded builds -- see
+tests/schema_registry/conftest.py.
+"""
+
+
+def test_config_encrypt_executor():
+    executor = FieldEncryptionExecutor()
+    client_conf = {'url': 'mock://'}
+    rule_conf = {'key': 'value'}
+    executor.configure(client_conf, rule_conf)
+    # configure with same args is fine
+    executor.configure(client_conf, rule_conf)
+    rule_conf2 = {'key2': 'value2'}
+    # configure with additional rule_conf keys is fine
+    executor.configure(client_conf, rule_conf2)
+
+    client_conf2 = {
+        'url': 'mock://',
+        'ssl.key.location': '/ssl/keys/client',
+        'ssl.certificate.location': '/ssl/certs/client',
+    }
+    with pytest.raises(RuleError, match="executor already configured"):
+        executor.configure(client_conf2, rule_conf)
+
+    rule_conf3 = {'key': 'value3'}
+    with pytest.raises(RuleError, match="rule config key already set: key"):
+        executor.configure(client_conf, rule_conf3)