PR Checklist

• Have you checked if it works normally in all models? Ignore this if it doesn't use models.
• Have you checked if it works normally in all web, local, and node hosted versions? If it doesn't, have you blocked it in those versions?
• Have you added type definitions?

Description

This PR introduces new LUA API functions to retrieve and embed character and persona images.

• getCharacterImage(triggerId): Writes the character's image to the inlay and returns a string for the embedded image (e.g., {{inlayed::asset/abc...123.png}}).
• getPersonaImage(triggerId): Does the same for the persona's image.

This is primarily useful for providing reference images to an LLM, such as sending a character's reference image to a model like gemini-2.5-flash-image-preview.

Both functions return nil if the image is not available.