fix: pass reference images to Codex image generation

[nikzolahr]

Summary

• expose optional reference_image_paths on the Hermes image_generate tool schema
• forward reference images through image plugin dispatch into the provider kwargs
• teach the OpenAI Codex image generation plugin to send local/URL reference images as input_image items
• return a clear unsupported-reference error when references are provided without a reference-capable plugin

Test Plan

• python -m pytest tests/tools/test_image_generation.py tests/tools/test_image_generation_plugin_dispatch.py tests/plugins/image_gen/test_openai_codex_provider.py -q -o 'addopts='

[alt-glitch]

Duplicate of #15308 and #21854 — both add optional reference image support to image_generate with openai-codex provider opt-in. Same feature, same code paths.

[kshitijk4poor]

Closing as a duplicate — Codex OAuth image-to-image / reference-image input is now on main via #57017 (merge commit 019950560).

That PR wires source/reference images through the Codex Responses input_image path on the unified image_generate surface, with magic-byte validation, a 25MB cap, the agent.file_safety read guard, and a 16-image clamp. Your PR tackled the same feature — thank you for the contribution and for helping surface how much demand there was for this. Credit to everyone in the cluster who pushed on it.

If you spot a gap in the merged implementation, please open a follow-up. 🙏