hxbrief: Nested operation should still apply any "non-transient" behaviour

The hxbrief behaviour can be split into two aspects

1. What is printed to the console while the child process is running
2. What ends up as hxbrief's stdout/stderr output once the child process has finished

The former we do not want in the case of nested operation, but the latter does make sense. Setting --lines 0 is a good first approach, but not sufficient, because a) we still would have a status line b) strictly speaking we may be delaying certain output more than strictly necessary, arguably buggy behaviour c) for some reason there is some other bug as well that leads some additional output.

Not sure if the whole thing is worth implementing. But let's keep it just to document the current behaviour and the problems one might run into.

Start at the hxbrief entry point and trace how nested operation handles --lines 0, the status line, and child-process output. Done means nested runs suppress transient console output while preserving the intended final stdout/stderr behavior without unnecessary delay or extra output.