This PR adds a comprehensive model card for SphereAR, the model presented in [Hyperspherical Latents Improve Continuous-Token Autoregressive Generation](https://huggingface.co/papers/2509.24335).
It includes:
- A description of the model based on the paper abstract and GitHub README.
- The `pipeline_tag: text-to-image` for discoverability on the Hub.
- A link to the paper and the official GitHub repository.
- A table of available model checkpoints.
- A sample usage snippet for image generation, adapted from the official GitHub repository.
- The BibTeX citation for the paper.
Please review and merge this PR if everything looks good.
