refactor: use GraphQL string scalar for KSUID transit

Marshal and unmarshal both use the base62 KSUID string, replacing the
legacy JSON object wrapper and aligning gqlgen scalar behavior.

Co-authored-by: Cursor <cursoragent@cursor.com>

ksuid_gql.go

@@ -1,17 +1,13 @@
 package dbx
 
 import (
-	"encoding/json"
 	"fmt"
 	"io"
+	"strconv"
 
 	"github.com/segmentio/ksuid"
 )
 
-type ksuidGQLTransport struct {
-	KSUIDStr string `json:"ksuid_str"`
-}
-
 func unmarshalKSUIDFromGQL(value any, unmarshal func([]byte) error) error {
 	str, ok := value.(string)
 	if !ok {
@@ -20,14 +16,11 @@ func unmarshalKSUIDFromGQL(value any, unmarshal func([]byte) error) error {
 	return unmarshal([]byte(str))
 }
 
+// marshalKSUIDToGQL writes a JSON-encoded string scalar for gqlgen.
 func marshalKSUIDToGQL(w io.Writer, id ksuid.KSUID) {
-	transport := ksuidGQLTransport{KSUIDStr: id.String()}
-	data, err := json.Marshal(transport)
-	if err != nil {
-		panic(fmt.Errorf("GraphQL failed to JSON-marshal KSUID value: %s", err))
-	}
-	if _, err := w.Write(data); err != nil {
-		panic(fmt.Errorf("GraphQL failed to write KSUID value: %s", string(data)))
+	quoted := strconv.Quote(id.String())
+	if _, err := io.WriteString(w, quoted); err != nil {
+		panic(fmt.Errorf("GraphQL failed to write KSUID value: %w", err))
 	}
 }