fix: Fix InputTokensDetails validation in OpenAI responses test and formatting in a2a_agent_executor

- Add missing `cache_write_tokens=0` to `InputTokensDetails` in `test_openai_responses_llm.py` to fix validation error with newer openai SDK versions.
- Remove extra empty line after `END_INTERNAL` in `a2a_agent_executor.py` to prevent double empty lines after Copybara export.

Co-authored-by: Shangjie Chen <deanchen@google.com>
PiperOrigin-RevId: 945326642

Author: DeanChensj

src/google/adk/a2a/executor/a2a_agent_executor.py

@@ -44,7 +44,6 @@
 from .utils import execute_after_event_interceptors
 from .utils import execute_before_agent_interceptors
 
-
 logger = logging.getLogger('google_adk.' + __name__)
 
 

tests/unittests/labs/openai/test_openai_responses_llm.py

@@ -672,7 +672,9 @@ def test_response_parsing_accepts_openai_sdk_response_types():
       status='completed',
       usage=ResponseUsage(
           input_tokens=3,
-          input_tokens_details=InputTokensDetails(cached_tokens=1),
+          input_tokens_details=InputTokensDetails(
+              cached_tokens=1, cache_write_tokens=0
+          ),
           output_tokens=5,
           output_tokens_details=OutputTokensDetails(reasoning_tokens=2),
           total_tokens=8,