fix: Remove accidental shell commands example changes (#13094)
## Why
The previous PTY shutdown fix accidentally changed the
`with-shell-commands` example. That example should stay focused on shell
command usage and not include the manual signal repro.
## What
Removes the accidental example `dev` script, task configuration, and
signal-counting helper script.
## How
Verified the diff is limited to `examples/with-shell-commands`. Pre-push
hooks ran successfully during `git push`.
