[feature] AI Copilot - JSON schema generated by AI when defining the structured output

As a Workflow Developer
I want to define JSON schema by using AI to analyze the prompt and then generate JSON schema for the structured output
So that I can quickly define JSON schema just by specifying the prompt

UI idea:
https://share.cleanshot.com/2qq2KBjw

Start by reviewing the linked UI idea and tracing the existing structured-output and JSON schema flow in the project. Define the interaction that accepts a prompt and produces a usable schema, then verify that the generated schema appears correctly in the structured-output configuration.

Written by the indexing model from the issue text.