7a2980e2f1
Review follow-ups: the warning now carries only the two endpoint URIs and the status code — attaching the exception object would let any real sink render its ToString(), which for RpcException includes server-authored Status.Detail. The leak pin test now also asserts no exception rides on the warning, via a new WarningExceptions capture on RecordingLogger. Plus two cosmetic nits: unified ThrowIfNull idiom, documented that FallbackEndpoints mutation after Validate is unsupported. Claude-Session: https://claude.ai/code/session_014WNM4vjoVksyyBraTXSZE1