Add schema validation in src/parser.ts that checks: enum fields have a non-empty values array, object fields have a fields array, array fields have an items definition, and primary/unique aren't both set incorrectly. On invalid schema, schema-cast generate should exit non-zero with a specific, actionable error message (file, field name, what's wrong) instead of failing generically or generating broken output.
Add schema validation in src/parser.ts that checks: enum fields have a non-empty values array, object fields have a fields array, array fields have an items definition, and primary/unique aren't both set incorrectly. On invalid schema, schema-cast generate should exit non-zero with a specific, actionable error message (file, field name, what's wrong) instead of failing generically or generating broken output.