Validate Anthropic SDK v2 compatibility for the ML extra #2474

Problem

EventRelay PR #2465 permits Anthropic SDK 2.x through the ml extra. The lockfile was out of sync with pyproject.toml, and the standard Python CI job installs .[dev,youtube], so that job does not by itself prove the ml path works with SDK 2.x.

Completion criteria

• Keep pyproject.toml and uv.lock synchronized with the CI-pinned uv version.
• Exercise the Anthropic 2.x client surfaces used by UnifiedAISDK, tri_model_consensus_tool, and AnthropicAdapter with focused tests or a reproducible compatibility check; preserve request and response behavior.
• If compatibility cannot be established, retain the previous <2 bound until the callers are adapted.
• Verify the exact PR head's required checks and review findings before merge.

Tracked by #2465. Merging the completed PR should close this issue.