chore(model gallery): add mistralai_magistral-small-2509

[mudler]

Description

This pull request adds a new model entry for Magistral Small 1.2 to the gallery/index.yaml file, expanding the available model options for local deployment. The addition includes detailed metadata, download URLs, a description, and file information.

New model addition:

• Added a new entry for mistralai_magistral-small-2509, including its name, description, and relevant Hugging Face URLs. This model builds upon Mistral Small 3.2, with enhanced reasoning capabilities and efficient deployment for local hardware.
• Specified model parameters and overrides, ensuring correct configuration for local use.
• Included file details for the quantized GGUF version, with SHA256 checksum and Hugging Face URI for reliable retrieval.
  Notes for Reviewers

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