argv for mix cerbero.snapshot: --url | --emit-sql | --from-file, --out, --config, --migration-source, --precision, --engine (postgres | cockroachdb; steers --emit-sql only — the live path detects the engine from the connection and --from-file from the file's own sections).
Loads .cerbero.exs (or the path given via --config) the same way
mix cerbero.check does, so config.schemas governs which schemas the
exporter reads instead of the connection always being hardcoded to
["public"], and config.precision selects the export mode
(--precision exact|order_of_magnitude overrides it). A bad config or an
invalid precision is an operational error (exit 2), same category as an
unreachable database.
--out defaults to config.snapshot_path, so the exported snapshot lands
exactly where mix cerbero.check reads it.