Problem

Gateway session mutation authorization has two independent gates:

1. the method registry and dynamic scope resolver authorize the negotiated
   operator scopes; then
2. a session-handler guard rejects clients classified as WebChat by client ID
   or mode, regardless of those approved scopes.

The only identity exception is openclaw-control-ui. That makes a
client-reported product label part of authorization and encourages third-party clients
to impersonate Control UI. PinchChat added a configurable client ID for this
workaround in
e8fe332.

Options

A. Authorize session mutations by negotiated scopes

Remove the WebChat identity guard. Keep the existing method policy:

• operator.write for lower-risk mutations such as organizational patch fields,
  checkpoint branch, and fork;
• operator.admin for destructive or high-risk mutations such as unrestricted
  delete, compact, restore, rewind, branch switching, dispatch, and reclaim;
• parameter-aware dynamic scope checks for patch and delete.

B. Keep the identity policy

Document a client ID/mode policy matrix and return a structured policy error.
This preserves the restriction but keeps authorization dependent on a
client-reported product identity.

Decision

Choose Option A. Negotiated scopes are the authorization contract. Client ID and
mode remain product/connection metadata, not a second session mutation ACL.

This does not change connection admission, device pairing, scope approval, or
gateway.controlUi.dangerouslyDisableDeviceAuth. No protocol or config surface
changes.

Acceptance

• Read-only WebChat clients receive the normal structured missing-scope errors.
• Admin-scoped WebChat clients can perform authorized session mutations without
  using the Control UI client ID.
• Every formerly identity-blocked mutation remains classified in the central
  method scope registry.
• Operator-scope docs and the changelog describe the contract.