Stop freezing the xAI/xAI-OAuth catalog at import so /model and setup
pick up new Grok IDs after the models.dev cache refreshes. Put xai and
xai-oauth on the shared picker-time models.dev merge path and pin
grok-4.6 as the default headline model.
The model is callable via xAI OAuth but omitted from models.dev and
/v1/models listings. Merge it into the curated xAI catalog so it appears
in `hermes model` without requiring a custom model name.