'ccs bar install' previously ended with two manual steps: clearing the
Gatekeeper quarantine by hand and running 'ccs bar' separately.
Install now detects an existing installation and says so before
reinstalling, clears the quarantine attribute itself via execFile with
a graceful fallback to the printed hint when xattr fails, and ends with
a TTY-aware 'Launch CCS Bar now?' prompt (default yes) that hands off
to the existing launch flow. --launch forces the handoff and
--no-launch suppresses it for scripted installs; non-TTY runs skip the
prompt and print the manual command instead.
Closes#1504
Tam Nhu Tran
4eef3f77a4