Tasks
* #3538174 Use streamed chat for agents

Bugs
* #3586077 AiFunctionCall plugins trigger ExecutableInterface::execute() deprecation notice
* #3586079 Agent exceptions during LLM calls are silently swallowed, making error handling difficult

Contributors:
marcus_johansson, a.dmitriiev, abhisekmazumdar, nikro, akhil babu, cadence96, ahmad khader, narendrar