test(drawdb): add test for converting column types with modifiers

* Implement tests to ensure explicit type modifiers are preserved during conversion.
* Validate behavior for varchar, numeric, and custom vector types.

pkg/writers/bun/writer_test.go

@@ -698,3 +698,23 @@ func TestTypeMapper_BuildBunTag(t *testing.T) {
 		})
 	}
 }
+
+func TestTypeMapper_BuildBunTag_PreservesExplicitTypeModifiers(t *testing.T) {
+	mapper := NewTypeMapper()
+
+	col := &models.Column{
+		Name:      "embedding",
+		Type:      "vector(1536)",
+		Length:    1536,
+		Precision: 0,
+		Scale:     0,
+	}
+
+	tag := mapper.BuildBunTag(col, nil)
+	if !strings.Contains(tag, "type:vector(1536),") {
+		t.Fatalf("expected explicit modifier to be preserved, got %q", tag)
+	}
+	if strings.Contains(tag, ")(") {
+		t.Fatalf("type modifier appears duplicated in %q", tag)
+	}
+}