Egress gateway rename (was "upstream proxy")

The internal MCP-proxy infrastructure was renamed end-to-end:

• New endpoints: /v1/code/egress/gateway (was /v1/code/upstreamproxy/...) and /v2/session_ingress/mcp/ws/.
• All log lines moved from [upstreamproxy] ... to [egress-gateway] ... (e.g. [egress-gateway] enabled on 127.0.0.1:, [egress-gateway] relay listening on 127.0.0.1:, [egress-gateway] aws config write failed: ..., [egress-gateway] prctl unavailable: ..., [egress-gateway] no session token; proxy disabled, [egress-gateway] ws error: ...).
• The internal initEgressGateway / getEgressGatewayEnv / registerEgressGatewayEnvFn exports replace the UpstreamProxy names.
• Init failures now log [init] egress gateway init failed: ...; continuing without proxy.

If you scrape Claude Code logs for the old upstreamproxy prefix, update your queries.