vix run does not stream stdout in real time

[GaspardKirira]

Problem

When running long-lived programs (e.g. servers) with vix run, stdout is sometimes not displayed immediately.

Example:

std::cout << "[server] started\n";

Logs may not appear until later, making it look like the process is stuck.

Expected

Logs should appear in real time, like when running the binary directly.

Notes

Using std::endl or std::flush fixes it, which suggests a buffering issue.