chore(vendor): sync streaming latency monotonic timing

[sayonfortify]

Vendors fr-openllmetry-py tag fr-v0.52.6.31 into ocelle.

What changed:

• Vendor manifest moves from fr-v0.52.6.30 to fr-v0.52.6.31.
• Carries the SDK fix from openllmetry-py#42: TTFT/STTG elapsed-time measurements use monotonic perf_counter-based clocks and clamp negative elapsed values to zero.
• Touched vendored provider paths: OpenAI, Anthropic, Bedrock, LiteLLM, LangChain.
• Google GenAI and LlamaIndex already used perf_counter + clamp and are unchanged by this tag.

Validation:

• ./scripts/vendor.sh ../fr-openllmetry-py . fr-v0.52.6.31
• python3 -m py_compile on changed vendored provider files
• conda run -n py3.12 python -m pip install -e .
• conda run -n py3.12 python -m pytest tests/test_vendored_imports.py -q -> 34 passed