fix: enforce atomic agent registration contract

sdks/node/src/client.ts

@@ -28,6 +28,7 @@ import type {
   ErrorResponse,
 } from './types.js';
 import { ElydoraError } from './errors.js';
+import { assertIntegrationType } from './integration-types.js';
 import {
   jcsCanonicalise,
   computePayloadHash,
@@ -148,6 +149,7 @@ export class ElydoraClient {
   // -------------------------------------------------------------------------
 
   async registerAgent(request: RegisterAgentRequest): Promise<RegisterAgentResponse> {
+    assertIntegrationType(request?.integration_type);
     return this.request<RegisterAgentResponse>('POST', '/v1/agents/register', request);
   }