refactor(pkg): canonicalize base types and adjust length handling

* Update base types to keep explicit modifier forms
* Modify length handling for vector types in tests

pkg/readers/gorm/reader.go

@@ -804,6 +804,7 @@ func (r *Reader) parseTypeWithLength(typeStr string) (baseType string, length in
 		// This avoids converting custom modifiers like vector(1536) into Length.
 		if pgsql.SupportsLength(rawBaseType) && !strings.Contains(parens, ",") {
 			if _, err := fmt.Sscanf(parens, "%d", &length); err == nil {
+				baseType = pgsql.CanonicalizeBaseType(rawBaseType)
 				return
 			}
 		}