improve container-client tests

[anonrig]

Extracted from #4371

[ask-bonk]

Minor test improvements (safer shell commands, Promise.withResolvers, timeout for WebSocket test). One concern about removing the monitor() call.

[ask-bonk]

I'm Bonk, and I've done a quick review of your PR.

This PR improves container-client tests by: making the Docker cleanup command safer (pipe to xargs -r instead of subshell), fixing the test target name in the README, removing noisy retry logs, modernizing to Promise.withResolvers, and adding a 5-second timeout to the WebSocket message wait.

Issues found (1):

1. Missing monitor() call after start() in testInterceptWebSocket — The PR removes container.monitor().finally(...) entirely, but the file header explicitly warns that monitor() must be called after start() to avoid losing track of container lifetime. Every other test method follows this pattern. Posted a suggestion to keep the monitor() call while dropping the .finally() log.

github run

[dom96]

Looks good!