Instead of silently writing ~/.mackup/ssr-*.cfg on every sync, generation
is now an explicit opt-in command: ssr mackup scan
ssr mackup scan — dry-run: shows NEW/UPD/DEL changes, prompts before writing
ssr mackup list — list existing generated files
ssr mackup clean — remove all generated files (with confirmation)
ssr sync no longer calls generate_custom_cfg automatically.
Completions updated for zsh, bash, fish.
Co-authored-by: Cursor <cursoragent@cursor.com>
