docs(gateway): stage QR client capability

docs/gateway/clients.md

@@ -136,35 +136,10 @@ snapshot, so re-read them on every reconnect.
 
 ### Present system-agent QR codes
 
-Advertise `GATEWAY_CLIENT_CAPS.SYSTEM_AGENT_QR_CODE` only when the client can
-render a QR image and return a deliberate acknowledgement. A pending
-`openclaw.chat` response can then carry a QR `step` through the same wizard-step
-contract used for other setup controls:
-
-```json
-{
-  "step": {
-    "id": "setup-qr",
-    "type": "qr",
-    "title": "Scan QR code",
-    "message": "Scan the code, then continue.",
-    "qrDataUrl": "data:image/png;base64,...",
-    "expiresInMs": 120000,
-    "executor": "client"
-  }
-}
-```
-
-`qrDataUrl` is no longer than 16,384 characters. `expiresInMs` is the remaining
-lifetime when the Gateway emits the response, so remote clients never compare
-the Gateway clock with their own. Acknowledge it with
-`wizardAnswer: { "stepId": "setup-qr" }`.
-
-Keep the QR visible only while that step remains unresolved and for at most
-`step.expiresInMs` after receipt. At the deadline, remove both the image and
-acknowledgement action. Discard the image bytes after a confirmed or
-delivery-uncertain acknowledgement. Clients that do not advertise the
-capability retain the prose fallback and never receive a QR step.
+`GATEWAY_CLIENT_CAPS.SYSTEM_AGENT_QR_CODE` and the QR wizard-step shape are
+reserved until system-agent QR production and Gateway projection are both
+available. Clients should not advertise this capability yet; the contract alone
+does not make existing Gateway methods emit QR steps.
 
 ## Recover state after reconnect