The CLI's native Git runner and the server's run_git_plan each hand-rolled
the same mechanics: kill-on-drop, a wall-clock timeout, output capture,
and (only in the CLI) process-group teardown, bounded capture, and
cancellation. Add fabro_proc::SupervisedCommand, which owns stdio, the
process group, the timeout, cooperative cancellation, and bounded
capture, and put both runners on it. The server gains group teardown on
timeout, so helpers a stuck clone or fetch spawned no longer outlive it;
the CLI keeps discarding output on failure and gains nothing but less
code. The hardened -c overrides become one named list in the CLI.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
