feat: stamp gateway attribution metadata

[haasonsaas]

Summary

• add team, workload, session, and evidence attribution headers to the Anthropic shim
• pass the new attribution options through sync and async Python clients and the TypeScript client
• keep org/principal/trace behavior backward compatible

Tests

• npm test
• npm run typecheck
• .venv/bin/python -m pytest tests

[cursor]

PR Summary

Low Risk
Low risk: additive, optional request headers and constructor options with updated tests; no changes to auth flow or core request logic beyond extra metadata.

Overview
Adds support for stamping additional EvalOps attribution headers—X-EvalOps-Team-ID, X-EvalOps-Workload, X-EvalOps-Session-ID, and X-EvalOps-Evidence-ID—sourced from new constructor/options fields or the corresponding EVALOPS_* env vars.

Threads these new options through the Python Anthropic/AsyncAnthropic clients and the TypeScript EvalOpsAnthropic client via build_evalops_headers/buildEvalOpsHeaders, and updates unit tests to assert the new headers are present while keeping existing org/principal/trace behavior intact.

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