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

README.md

@@ -164,7 +164,12 @@ type, selected via `--types sqltypes`. See the
 [`pkg/sqltypes` README](./pkg/sqltypes/README.md) for the full type
 reference, or the [`bun`](./pkg/writers/bun/README.md) /
 [`gorm`](./pkg/writers/gorm/README.md) writer docs for the `--types` flag
-(`sqltypes`, `stdlib`, or `baselib`).
+(`sqltypes`, `stdlib`, or `baselib`). PostgreSQL array columns are the one
+exception: the `bun` writer always generates native Go slices (`[]string`,
+`[]int32`, …) with an explicit `array` bun tag, regardless of `--types` —
+see [`bun`'s `--array-nullable`](./pkg/writers/bun/README.md#nullablearrays)
+flag for nullable-array handling. The `SqlXxxArray` wrapper types remain
+available in `pkg/sqltypes` and are still used by the `gorm` writer.
 
 ## Contributing