Restore consolidated final responses for non-streaming

[contextablemark]

Summary

• reinstate consolidated START/CONTENT/END emission for final responses when no stream is active while keeping duplicate suppression
• ensure empty or duplicate final responses still clean up state without emitting events
• update translator tests to expect non-streaming consolidated responses and verify de-duplication behavior

Testing

• PYTHONPATH=sdks/python:integrations/adk-middleware/python/src python -m pytest integrations/adk-middleware/python/tests/test_event_translator_comprehensive.py -k "final_response_no_streaming or final_response_from_agent_callback or final_response_closes_stream_without_consolidated_text" -q (fails: ModuleNotFoundError: No module named 'google')

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Codex Task