model : add support for Phi4ForCausalLMV (#20168)
* Add support for Phi4ForCausalLMV.
* Fix Phi-4 vision parity (correcting SigLIP2 patch-kernel export layout) and matching HF NaFlex resize behavior in mtmd.
* Rename contants + fix tokenizer label
* Clean-ups.
* Fix GGUF export.
* Set tokenizer.ggml.pre explicitly.
* Default vocab name rather than forcing it.
* Clean-ups.
* Fix indent.
* Fix subscriptable error.
* remov overcomplicated code path
* Clean-ups.
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Co-authored-by: Xuan Son Nguyen <son@huggingface.co>
