hermes - 💡(How to fix) Fix feat: extend image_gen schema to accept reference_image_urls for multi-modal models (e.g. UNI 1.1)

Problem

The current image_gen tool schema is text-only — it does not accept reference_image_urls. This means models like Luma UNI 1.1 (which fundamentally require reference images for brand-aligned generation) cannot be properly implemented as image_gen plugins.

Proposed Change

Extend the image_gen tool schema and any associated ABC to accept:

reference_image_urls: Optional[List[str]] = None

Motivation

Mother (an AI marketing platform) needs UNI 1.1 as an image_gen plugin for brand-memory-aware image generation. Currently forced to implement as a Mother-tools MCP wrapper instead of a proper Hermes plugin due to this gap. Would collapse that workaround when this FR lands.