fix(tests): stabilize 3 failing CI tests

1. Add missing __init__.py files in tests/test_litellm/llms/gemini/ and
   subdirectories (realtime/, image_edit/) to fix ModuleNotFoundError
   with pytest-xdist parallel workers.

2. Update test_transform_request_uses_dynamic_max_tokens to use
   claude-3-7-sonnet-20250219 (max_output_tokens=64000) since
   claude-3-5-sonnet-20241022 was removed from model_prices JSON
   during deprecated model cleanup. The test assertion was outdated.

3. Update context caching TTL tests to use gemini-2.5-pro instead of
   gemini-1.5-pro. The old model was removed from model_prices JSON,
   causing supports_system_messages to return False, which prevented
   system_instruction from appearing in the transformation output.

Co-authored-by: yuneng-jiang <yuneng-jiang@users.noreply.github.com>

tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py

@@ -1932,16 +1932,16 @@ def test_transform_request_uses_dynamic_max_tokens():
 
     messages = [{"role": "user", "content": "Hello"}]
 
-    # Claude 3.5 model should get 8192 as default max_tokens
+    # Claude 3.7 model should get 64000 as default max_tokens (from model_prices_and_context_window.json)
     result = config.transform_request(
-        model="claude-3-5-sonnet-20241022",
+        model="claude-3-7-sonnet-20250219",
         messages=messages,
         optional_params={},  # No max_tokens provided
         litellm_params={},
         headers={}
     )
 
-    assert result["max_tokens"] == 8192
+    assert result["max_tokens"] == 64000
 
 
 def test_transform_request_respects_user_max_tokens():
@@ -1955,7 +1955,7 @@ def test_transform_request_respects_user_max_tokens():
 
     # User provides explicit max_tokens=1000, should not be overridden
     result = config.transform_request(
-        model="claude-3-5-sonnet-20241022",
+        model="claude-3-7-sonnet-20250219",
         messages=messages,
         optional_params={"max_tokens": 1000},
         litellm_params={},

tests/test_litellm/llms/vertex_ai/context_caching/test_context_caching_ttl.py

@@ -211,7 +211,7 @@ class TestTransformationWithTTL:
         vertex_project="test_project"
         
         result = transform_openai_messages_to_gemini_context_caching(
-            model="gemini-1.5-pro",
+            model="gemini-2.5-pro",
             messages=messages,
             cache_key="test-cache-key",
             custom_llm_provider=custom_llm_provider,
@@ -223,9 +223,9 @@ class TestTransformationWithTTL:
         assert result["ttl"] == "3600s"
 
         if custom_llm_provider == "gemini":
-            assert result["model"] == "models/gemini-1.5-pro"
+            assert result["model"] == "models/gemini-2.5-pro"
         else:
-            assert result["model"] == f"projects/{vertex_project}/locations/{vertex_location}/publishers/google/models/gemini-1.5-pro"
+            assert result["model"] == f"projects/{vertex_project}/locations/{vertex_location}/publishers/google/models/gemini-2.5-pro"
         
 
         assert result["displayName"] == "test-cache-key"
@@ -250,7 +250,7 @@ class TestTransformationWithTTL:
         vertex_project="test_project"
         
         result = transform_openai_messages_to_gemini_context_caching(
-            model="gemini-1.5-pro", 
+            model="gemini-2.5-pro", 
             messages=messages,
             cache_key="test-cache-key",
             custom_llm_provider=custom_llm_provider,
@@ -261,9 +261,9 @@ class TestTransformationWithTTL:
         assert "ttl" not in result
 
         if custom_llm_provider == "gemini":
-            assert result["model"] == "models/gemini-1.5-pro"
+            assert result["model"] == "models/gemini-2.5-pro"
         else:
-            assert result["model"] == f"projects/{vertex_project}/locations/{vertex_location}/publishers/google/models/gemini-1.5-pro"
+            assert result["model"] == f"projects/{vertex_project}/locations/{vertex_location}/publishers/google/models/gemini-2.5-pro"
         
         assert result["displayName"] == "test-cache-key"
     
@@ -286,7 +286,7 @@ class TestTransformationWithTTL:
         vertex_project="test_project"
         
         result = transform_openai_messages_to_gemini_context_caching(
-            model="gemini-1.5-pro",
+            model="gemini-2.5-pro",
             messages=messages, 
             cache_key="test-cache-key",
             custom_llm_provider=custom_llm_provider,
@@ -297,9 +297,9 @@ class TestTransformationWithTTL:
         assert "ttl" not in result
 
         if custom_llm_provider == "gemini":
-            assert result["model"] == "models/gemini-1.5-pro"
+            assert result["model"] == "models/gemini-2.5-pro"
         else:
-            assert result["model"] == f"projects/{vertex_project}/locations/{vertex_location}/publishers/google/models/gemini-1.5-pro"
+            assert result["model"] == f"projects/{vertex_project}/locations/{vertex_location}/publishers/google/models/gemini-2.5-pro"
         
         assert result["displayName"] == "test-cache-key"
     
@@ -332,7 +332,7 @@ class TestTransformationWithTTL:
         vertex_project="test_project"
         
         result = transform_openai_messages_to_gemini_context_caching(
-            model="gemini-1.5-pro",
+            model="gemini-2.5-pro",
             messages=messages,
             cache_key="test-cache-key",
             custom_llm_provider=custom_llm_provider,
@@ -345,9 +345,9 @@ class TestTransformationWithTTL:
         assert "system_instruction" in result
         
         if custom_llm_provider == "gemini":
-            assert result["model"] == "models/gemini-1.5-pro"
+            assert result["model"] == "models/gemini-2.5-pro"
         else:
-            assert result["model"] == f"projects/{vertex_project}/locations/{vertex_location}/publishers/google/models/gemini-1.5-pro"
+            assert result["model"] == f"projects/{vertex_project}/locations/{vertex_location}/publishers/google/models/gemini-2.5-pro"
         
         assert result["displayName"] == "test-cache-key"