🧹 [code health improvement] split long function test_complete_no_external_write_chain_uses_authenticated_roles

[joy7758]

🎯 What: The code health issue addressed is a "Long Function" in tests/test_runtime_mcp_end_to_end.py for test_complete_no_external_write_chain_uses_authenticated_roles.
💡 Why: Splitting this massive end-to-end integration test into smaller, logical blocks (_execute_initial_request and _execute_release_decision) significantly improves readability and reduces cognitive load, making the test easier to maintain and understand.
✅ Verification: Verified by ensuring no logic was altered during extraction and running the entire unittest suite (with necessary environment variables for MCP cloud keys) to confirm the specific test case and remaining tests still pass correctly. Additionally, formatting was verified using ruff.
✨ Result: A more modular and readable test file, with the single long function refactored to delegate phases of the execution to private helper methods.

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PR created automatically by Jules for task 4184416929279816458 started by @joy7758

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