test(grok): add isolated subscription product qualification

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.env.runner-e2e.example

@@ -9,3 +9,6 @@ DAYTONA_API_KEY=
 # Required only for Daytona cells. Use an immutable, anonymously pullable
 # digest from the Runner Full-Stack E2E image job or a locally published image.
 PAPERCLIP_E2E_DAYTONA_IMAGE=ghcr.io/paperclipai/paperclip-daytona-runner@sha256:REPLACE_ME
+# Optional, explicit subscription qualification only. Supply privately at runtime;
+# never commit an actual auth.json payload. API-key profiles do not use this value.
+# GROK_AUTH_JSON=