Mirror fuj infer's read-only mode: SyncOpts.DryRun skips WriteHeader,
AppendValues, and SortByDateColumn, printing one "Dry run: would …"
line per planned operation instead. ID-dedup still runs so the output
reflects exactly what the next real sync would write.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
