- Replace env var control (FASTSYNC_SOURCE_DIR, FASTSYNC_DEST_DIR,
FASTSYNC_SAVE_TO_DISK) with explicit --source-dir, --dest-dir,
--save-to-disk CLI arguments
- Keep env vars as fallback for backward compatibility
- Fix test.py: split '-c 0' into separate args ['-c', '0']
- Fix test.py: throttled suite failed because systemd-run didn't
inherit env vars; now all settings are passed as CLI args
- Add env_name to exception/timeout result entries for correct display
