models : dedup Kimi Linear delta net implementation (#19668)

models : dedup Kimi Linear delta net implementation (#19668)

* models : add llm_build_delta_net_base

* cont : keep qwen35 and qwen35moe graphs intact

* cont : add comments [no ci]

* add kimi linear to delta-net-base

* removed unnecessary ggml_cont from g_exp_t

* removed ggml_cont from g_diff_exp_t. moved ggml_cont for o to kimi-linear.cpp

* removed unnecessary diag mask

* cont : simplify

* cont : avoid graph splits

* scale q after mul instead of beginning

* scale q after mul instead of beginning

* identical ppl

* cont : fix scale and decay mask

* minor : remove TODO

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Co-authored-by: Georgi Gerganov <redacted>