llama : Support llama 4 text-only (#12791)
* llama4 conversion
* initial support, no chat template
* clean up a bit
* fix tokenizer conversion
* correct hparams
* try this
* fix shexp
* ffn_inp_normed
* chat template
* clean up model conversion
* add_bos
* add scale_before_ffn
* fix order
* weight_before_ffn
* llm_graph_input_attn_temp
* add chunk attn mask
* build_inp_attn_scale()
* add comment about ggml_repeat
* clarify comments
* fix build
