fix(writer): update nullable type handling to use baselib

* change default nullable type from resolvespec to baselib
* update type mappings in tests to reflect new nullable types
* adjust comments for clarity on nullable type options

pkg/writers/writer.go

@@ -24,12 +24,17 @@ type Writer interface {
 // in code-generation writers (Bun, GORM).
 const (
 	// NullableTypeResolveSpec uses github.com/bitechdev/ResolveSpec/pkg/spectypes
-	// (SqlString, SqlInt32, SqlVector, SqlStringArray, …). This is the default.
+	// (SqlString, SqlInt32, SqlVector, SqlStringArray, …).
 	NullableTypeResolveSpec = "resolvespec"
 
 	// NullableTypeStdlib uses the standard library database/sql nullable types
 	// (sql.NullString, sql.NullInt32, …) and plain Go slices for arrays.
 	NullableTypeStdlib = "stdlib"
+
+	// NullableTypeBaselib uses plain Go pointer types for nullable columns
+	// (*string, *int32, *time.Time, …) and plain Go slices for arrays.
+	// No external imports are required beyond the standard library. This is the default.
+	NullableTypeBaselib = "baselib"
 )
 
 // WriterOptions contains common options for writers
@@ -49,6 +54,7 @@ type WriterOptions struct {
 	// code-generation writers (bun, gorm). Accepted values:
 	//   "resolvespec" (default) — github.com/bitechdev/ResolveSpec/pkg/spectypes
 	//   "stdlib"                — database/sql (sql.NullString, sql.NullInt32, …)
+	//   "baselib"               — plain Go pointer types (*string, *int32, …)
 	NullableTypes string
 
 	// Prisma7 enables Prisma 7-specific output for Prisma writers.