fix(parallel_installer): reset tty after cask installs

Cask installs can trigger interactive prompts (sudo, macOS security
frameworks) that write directly to /dev/tty without a trailing newline.
When running in parallel, the next worker's status message would append
to the same line as a stale "Password:" prompt, producing garbled output
like "Password:Using anykeyh.simplecov-vscode".

After the output lock is released following a cask install, write a
newline to /dev/tty to ensure the terminal cursor starts on a clean
line.  The write is a no-op in CI or when output is piped (ENXIO/ENOENT
are caught).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>