Fix enum columns cannot have auto_increment

Added validation to prevent enum columns from being used with auto_increment.
This matches MySQL behavior where auto_increment can only be used with numeric types.

Changes:
- Added ErrInvalidColumnSpecifier error message
- Added enum type validation in validateAutoIncrementModify and validateAutoIncrementAdd
- Enabled previously skipped test case for enum auto_increment validation

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: elianddb

enginetest/queries/script_queries.go

@@ -9000,7 +9000,7 @@ where
 		},
 	},
 	{
-		Skip:        true,
+		Skip:        false,
 		Name:        "enums with auto increment",
 		Dialect:     "mysql",
 		SetUpScript: []string{},

sql/analyzer/validate_create_table.go

@@ -791,6 +791,10 @@ func validateAutoIncrementModify(schema sql.Schema, keyedColumns map[string]bool
 	seen := false
 	for _, col := range schema {
 		if col.AutoIncrement {
+			// Check if column type is valid for auto_increment
+			if types.IsEnum(col.Type) {
+				return sql.ErrInvalidColumnSpecifier.New(col.Name)
+			}
 			// keyedColumns == nil means they are trying to add auto_increment column
 			if !col.PrimaryKey && !keyedColumns[col.Name] {
 				// AUTO_INCREMENT col must be a key
@@ -815,6 +819,10 @@ func validateAutoIncrementAdd(schema sql.Schema, keyColumns map[string]bool) err
 	for _, col := range schema {
 		if col.AutoIncrement {
 			{
+				// Check if column type is valid for auto_increment
+				if types.IsEnum(col.Type) {
+					return sql.ErrInvalidColumnSpecifier.New(col.Name)
+				}
 				if !col.PrimaryKey && !keyColumns[col.Name] {
 					// AUTO_INCREMENT col must be a key
 					return sql.ErrInvalidAutoIncCols.New()

sql/errors.go

@@ -669,6 +669,9 @@ var (
 	// ErrInvalidAutoIncCols is returned when an auto_increment column cannot be applied
 	ErrInvalidAutoIncCols = errors.NewKind("there can be only one auto_increment column and it must be defined as a key")
 
+	// ErrInvalidColumnSpecifier is returned when an invalid column specifier is used
+	ErrInvalidColumnSpecifier = errors.NewKind("Incorrect column specifier for column '%s'")
+
 	// ErrUnknownConstraintDefinition is returned when an unknown constraint type is used
 	ErrUnknownConstraintDefinition = errors.NewKind("unknown constraint definition: %s, %T")