feat(signals): type=inference exports without agent_id

[smirdha-source]

Summary

Documents the Signals export API change shipped in signals-api (cthulhu PR #180440, live in prod): POST /v1/signals/exports can now export Serverless Inference Signals conversations without an agent_id.

• CreateExportRequest: new optional type enum (agent | inference), same shape as CreateDeletionRequest.type. agent_id is no longer required; it is required when type is agent and must be omitted when type is inference. type defaults to agent when agent_id is provided and to inference when it is omitted.
• ExportJob: new type field.
• Operation description, request examples (agent + inference), cURL sample, and response examples updated.

Additive for existing clients: requests that send a real agent_id are unchanged, and the only new response field is type.

Testing

• make lint: bundle OK, Spectral 0 errors (remaining warnings are pre-existing in unrelated resources).
• Verified against production api.digitalocean.com: POST /v1/signals/exports with {"type":"inference", ...} → 201 with "type": "inference"; GET /v1/signals/exports/{id} and /download return the artifact.