fix(hybrid): close synchronous Runtime responses

[dajiaohuang]

Summary

• close synchronous streamed Runtime responses in a finally block on every return and exception path
• add focused regression coverage for both a successful SSE response and an HTTP error
• mirror the lifecycle handling already used by the incremental streaming endpoint

Fixes #257

Tests

• $env:PYTHONUTF8='1'; uv run --frozen --extra dev pytest -q tests/test_local_ui.py -k remote_ui (6 passed, 15 deselected)
• $env:PYTHONUTF8='1'; uv run --frozen --extra dev pytest -q (76 passed, 4 failed: the known evaluator regression addressed separately by fix(hybrid): accept refusal contractions in evaluator #256, plus 3 Windows failures because this host has no usable Bash/WSL execution for shell-script tests)
• uvx pre-commit run --show-diff-on-failure --color=never --files python/02-use-cases/hybrid_cloud_customer_service/local_ui.py python/02-use-cases/hybrid_cloud_customer_service/tests/test_local_ui.py