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/prisma_options.go

@@ -13,12 +13,13 @@ func newReaderOptions(filePath, connString string) *readers.ReaderOptions {
 	}
 }
 
-func newWriterOptions(outputPath, packageName string, flattenSchema bool, nullableTypes string, continueOnError bool) *writers.WriterOptions {
+func newWriterOptions(outputPath, packageName string, flattenSchema bool, nullableTypes, nullableArrays string, continueOnError bool) *writers.WriterOptions {
 	return &writers.WriterOptions{
 		OutputPath:      outputPath,
 		PackageName:     packageName,
 		FlattenSchema:   flattenSchema,
 		NullableTypes:   nullableTypes,
+		NullableArrays:  nullableArrays,
 		Prisma7:         prisma7,
 		ContinueOnError: continueOnError,
 	}