SDK: a null agent uuid in the create/update response becomes the string "None"

[mocha06]

Problem

AiAgentService.create_agent and AiAgentService.update_agent (packages/sdk/src/pipefy_sdk/services/ai_agent_service.py) check only that the response agent has a uuid key:

if not agent or "uuid" not in agent:
    raise ValueError(...)
agent_uuid = str(agent["uuid"])

If the API returns "uuid": null, the check passes and str(None) makes the UUID the string "None".

• create_agent returns agent_uuid: "None" as a success.
• PipefyClient.create_ai_agent then sends the chained update for the agent "None". That update fails, so the caller gets AiAgentConfigureError(agent_uuid="None"), which names an agent that does not exist.

Proposal

Reject a missing or null uuid with the existing ValueError in both methods: if not agent or not agent.get("uuid"). Add a test for each method with "uuid": None.

Context

Raised in the review of #704. The check predates that PR.