Consume Ki model queue updates in Ki node

[seanwevans]

Summary

• introduce a KiNodeState helper so Ki nodes retain the latest model parameters received from the coordinator
• extend the Ki node runtime to consume the ki_model_queue alongside the task queue and apply incoming ParameterPull updates
• add unit and integration coverage for the new model update path and clean up an unused import in the An node

Testing

• cargo fmt
• cargo test test_update_model_parameters (fails: database connection pool timeouts)

---

https://chatgpt.com/codex/tasks/task_e_68d829dc00088328a51b5300aa3391b5