fix(openclaw-bridge): use 'gateway-client'/'backend' as WS client id/mode

openclaw gateway validates client.id against a fixed set of known IDs.
Using a random UUID caused the connection to be rejected immediately with
'client/id must be equal to constant'. Use 'gateway-client' + 'backend'.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/openclaw-bridge/src/openclaw-client.ts

@@ -154,10 +154,10 @@ export class OpenClawClient {
         minProtocol: 3,
         maxProtocol: 3,
         client: {
-          id: this.deviceId,
+          id: 'gateway-client',
           version: '1.0.0',
           platform: 'node',
-          mode: 'channel',
+          mode: 'backend',
         },
         role: 'operator',
         scopes: ['operator.read', 'operator.write'],