* Fix pgsql reader double-quoting defaults: normalizePostgresDefault strips
surrounding SQL string literal quotes from column_default before storing,
matching the convention used by every other reader.
* Add NullableTypes field to WriterOptions with NullableTypeResolveSpec
(default) and NullableTypeStdlib constants.
* Both bun and gorm TypeMappers now accept a typeStyle parameter. stdlib
mode produces sql.NullString/NullInt32/NullTime etc. for nullable scalars,
plain Go slices for arrays, and time.Time for NOT NULL timestamps. Default
resolvespec behaviour is unchanged.
* Add --types flag to convert and split commands.
* Update bun/README.md and gorm/README.md with side-by-side generated code
examples, updated type mapping tables, and Writer Options documentation.
* Implement tests to ensure explicit type modifiers are preserved during conversion.
* Validate behavior for varchar, numeric, and custom vector types.
