feat!: replace rsyncwrapper with direct child_process.spawn

Remove the outdated rsyncwrapper dependency (unmaintained, uses
deprecated util._extend) and replace with a built-in buildRsyncCommand()
+ spawn implementation. Zero runtime dependencies.

BREAKING CHANGE: rsyncwrapper dependency removed, rsync command is now
constructed and executed directly via child_process.spawn.

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

Author: easingthemes