Arize Phoenix 20.7.0 migrates its MCP server to FastMCP 4 and the stateless protocol

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The 2026-09-03 release moves the Phoenix MCP server onto FastMCP 4 and the stateless protocol (#15903), makes AnalyticsSqlError a real exception instead of whatever it was (#15906), records the tool name on PXI LLM tool schemas (#15693), and lowers filtered trace queries with correlated scoping for performance (#15788). The separate phoenix-client 3.4.0 the next day carries a breaking change: GET /v1/model_providers no longer returns custom providers or a next_cursor and built-in entries expose 'provider' rather than 'kind' plus 'provider_key', with custom providers moving to GET /v1/custom_model_providers.