Variable useAgentGenerateConst Alpha

Generates content for a document (or specific fields) via Sanity Agent Actions.

• Uses instruction templates with $variables and supports instructionParams (constants, fields, documents, GROQ queries).
• Can target specific paths/fields; supports image generation when targeting image fields.
• Supports optional temperature, async, noWrite, and conditionalPaths.

Returns a stable callback that triggers the action and yields a Subscribable stream.