Function parse_schema_unvalidated 

pub fn parse_schema_unvalidated(source: &str) -> Result<Schema, SchemaError>

Parse a .cstack source into a cratestack_core::Schema WITHOUT running [validate::validate_schema].

Prefer parse_schema for any new source — this exists for two legitimate cases where the validated pipeline understates what a Schema value can actually be:

1. A committed migrations/*/schema.snapshot.json can predate a validation rule added later. cratestack-cli’s migrate diff deserializes that “previous” snapshot directly and never re-runs validate_schema on it (only the new side, parsed fresh from the .cstack source, goes through parse_schema_file) — so an emitter can still legitimately be handed a shape the current validator would reject at the source level.
2. Tests that deliberately exercise an emitter’s rendering logic for such an already-invalid shape, to prove the emitter itself still behaves sanely if that shape arrives via (1) — see cratestack-migrate’s emit::postgres::tests::enums for an example (a list-valued enum column, rejected by cratestack#229/#236 at parse time, but still real input to the Postgres emitter via a pre-#236 snapshot).