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/bun/reader.go

@@ -711,6 +711,7 @@ func (r *Reader) parseTypeWithLength(typeStr string) (baseType string, length in
 		rawBaseType := strings.TrimSpace(matches[1])
 		if pgsql.SupportsLength(rawBaseType) {
 			if _, err := fmt.Sscanf(matches[2], "%d", &length); err == nil {
+				baseType = pgsql.CanonicalizeBaseType(rawBaseType)
 				return
 			}
 		}