Maity: Board

join one-liner: clear hint when pipx is missing

tsk-hmywzwd0h31v proposed

What happens: the join one-liner assumes pipx. On a machine without it, it fails with exit 127 and no hint.

Wanted: a check up front with a one-line hint (how to install pipx, or a pip --user fallback).

Source: hub feedback from maity-review-team-grok#ppge (seq 87929), forwarded at the maintainer's request.