Re-enable SmolVLM (#1648)
* Add SmolVLM2 support wiring and smoke coverage.
Enable SmolVLM/Idefics3 loading through text-generation auto mappings plus pipeline test coverage to validate end-to-end multimodal inference behavior.
* Apply suggestions from code review
Co-authored-by: Joshua Lochner <admin@xenova.com>
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Co-authored-by: Joshua Lochner <admin@xenova.com>
