feat(bun): generate native Go array slices for PostgreSQL array columns

Bun's pgdialect scans/appends native slices directly, so array columns
(text[], integer[], uuid[], ...) always generate as plain []string,
[]int32, etc. with an explicit "array" bun tag, regardless of --types
(sqltypes/stdlib/baselib). The SqlXxxArray wrapper types are no longer
used for Bun array columns (gorm is unaffected and keeps using them).

Adds --array-nullable pointer_slice to represent nullable array columns
as *[]T instead of []T, so callers can distinguish SQL NULL (nil) from
'{}' (pointer to an empty slice). Verified end-to-end against a live
PostgreSQL instance for NULL/{}/populated arrays in every --types mode.

Closes #13

cmd/relspec/split.go

@@ -11,18 +11,19 @@ import (
 )
 
 var (
-	splitSourceType    string
-	splitSourcePath    string
-	splitSourceConn    string
-	splitTargetType    string
-	splitTargetPath    string
-	splitSchemas       string
-	splitTables        string
-	splitPackageName   string
-	splitDatabaseName  string
-	splitExcludeSchema string
-	splitExcludeTables string
-	splitNullableTypes string
+	splitSourceType     string
+	splitSourcePath     string
+	splitSourceConn     string
+	splitTargetType     string
+	splitTargetPath     string
+	splitSchemas        string
+	splitTables         string
+	splitPackageName    string
+	splitDatabaseName   string
+	splitExcludeSchema  string
+	splitExcludeTables  string
+	splitNullableTypes  string
+	splitNullableArrays string
 )
 
 var splitCmd = &cobra.Command{
@@ -112,6 +113,7 @@ func init() {
 	splitCmd.Flags().StringVar(&splitExcludeSchema, "exclude-schema", "", "Comma-separated list of schema names to exclude")
 	splitCmd.Flags().StringVar(&splitExcludeTables, "exclude-tables", "", "Comma-separated list of table names to exclude (case-insensitive)")
 	splitCmd.Flags().StringVar(&splitNullableTypes, "types", "", "Nullable type package for code-gen writers (bun/gorm): 'baselib' (default, Go pointer types), 'stdlib' (database/sql), or 'sqltypes'")
+	splitCmd.Flags().StringVar(&splitNullableArrays, "array-nullable", "", "Nullable PostgreSQL array representation for the Bun writer in stdlib/baselib --types mode: 'slice' (default, plain slice) or 'pointer_slice' (*[]T, distinguishes NULL from '{}')")
 
 	err := splitCmd.MarkFlagRequired("from")
 	if err != nil {
@@ -188,6 +190,7 @@ func runSplit(cmd *cobra.Command, args []string) error {
 		"",    // no schema filter for split
 		false, // no flatten-schema for split
 		splitNullableTypes,
+		splitNullableArrays,
 		false, // no continue-on-error for split
 		"",    // no extra fields for split
 	)