the sudo-unshare sandbox path runs the entire command as root, causing
files modified by shell commands (e.g. git merge) to become root-owned.
this breaks file_write/file_edit which run in the Node.js parent process
as the normal user (EACCES errors).
after PROC_CLEANUP (which needs root for umount/mount), drop back to
the original user via `su -p` so file operations match the uid of the
parent process. security-neutral: PID namespace isolation is the barrier,
not privilege level inside it.
Co-authored-by: Cursor <cursoragent@cursor.com>
Colin McDonnell