test(e2e): run host alias checks from docker

[pimlock]

Summary

• run the host alias e2e helper server in a Docker container published on the host instead of a local TcpListener
• add curl timeouts so host alias and inference-local failures stop quickly instead of hanging
• keep the direct host alias and inference.local coverage in the same e2e test file

Related Issue

• None

Changes

• update e2e/rust/tests/host_gateway_alias.rs to launch a Docker-backed HTTP server and clean it up automatically
• publish the helper server on a host port so host.openshell.internal resolves to something reachable in GitHub Actions job containers
• add --max-time 15 to sandbox curl invocations

Testing

• cargo test --manifest-path e2e/rust/Cargo.toml --features e2e --test host_gateway_alias

Checklist

• Tests added or updated
• Relevant tests passed
• No unrelated files included