Deploy model to Ray object store

Pre-load model weights into the Ray object store for fast access by plugins.

This operation:

1. Downloads the model archive from S3
2. Deserializes weights based on format (safetensors, pytorch, etc.)
3. Stores weights in Ray object store for zero-copy sharing

After deployment, plugins can load the model instantly using:

from engine.models.loader import load_namespace_model
weights = load_namespace_model("model_id")

Note: This is optional - models are also loaded on-demand when plugins first request them. Use this endpoint to pre-warm the cache.