SERIAL is accepted in FIELDS (...) and rejected in the parenthesised column list

[farhan-syah]

Two CREATE COLLECTION surfaces disagree on whether SERIAL is a column type.

CREATE COLLECTION a FIELDS (n SERIAL, v TEXT);
-- CREATE COLLECTION

CREATE COLLECTION b (n SERIAL, v TEXT);
-- ERROR: parse error: unknown column type: 'SERIAL' (SQLSTATE 42601)

The parenthesised form is the PostgreSQL-shaped spelling and the one a user reaches for. BIGSERIAL behaves the same way.

Expected

Both surfaces accept the same column types, or the rejected one names why it differs.

Notes

SERIAL expansion lives in parse_fields_clause_from_pairs and parse_fields_clause in control/server/shared/ddl/schema_validation.rs. Both expand SERIAL to INT DEFAULT nextval('<collection>_<field>_seq'). The parenthesised column-list parser resolves column types elsewhere and never sees that expansion.