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

pkg/writers/writer.go

@@ -37,6 +37,23 @@ const (
 	NullableTypeBaselib = "baselib"
 )
 
+// NullableArrays constants control how nullable PostgreSQL array columns are
+// represented in native-slice code-generation writers (Bun in stdlib/baselib
+// mode).
+const (
+	// NullableArraysSlice represents every array column (nullable or not) as
+	// a plain slice ([]string, []int32, …). SQL NULL and '{}' both scan into
+	// a zero-length/nil slice, so callers cannot distinguish them. This is
+	// the default.
+	NullableArraysSlice = "slice"
+
+	// NullableArraysPointerSlice represents nullable array columns as a
+	// pointer to a slice (*[]string, *[]int32, …), so callers can
+	// distinguish SQL NULL (nil pointer) from '{}' (pointer to an empty
+	// slice). NOT NULL array columns are unaffected and remain plain slices.
+	NullableArraysPointerSlice = "pointer_slice"
+)
+
 // WriterOptions contains common options for writers
 type WriterOptions struct {
 	// OutputPath is the path where the output should be written
@@ -57,6 +74,15 @@ type WriterOptions struct {
 	//   "baselib" (default)     — plain Go pointer types (*string, *int32, …)
 	NullableTypes string
 
+	// NullableArrays selects how nullable PostgreSQL array columns are
+	// represented in native-slice code-generation writers (bun). Accepted values:
+	//   "slice" (default)      — plain slice for every array column
+	//   "pointer_slice"        — pointer-to-slice for nullable array columns,
+	//                            distinguishing SQL NULL from '{}'
+	// Has no effect in "sqltypes" NullableTypes mode, which always uses the
+	// SqlXxxArray wrapper types.
+	NullableArrays string
+
 	// Prisma7 enables Prisma 7-specific output for Prisma writers.
 	Prisma7 bool