feat: support GLM 4.5 family of models

Author: sammcj

src/llama-model.cpp

@@ -1429,7 +1429,10 @@ void llama_model::load_hparams(llama_model_loader & ml) {
                 ml.get_key(LLM_KV_FIRST_K_DENSE_REPLACE,       hparams.first_k_dense_replace, 0);
 
                 // Expert gating function (GLM45 uses sigmoid)
-                ml.get_key(LLM_KV_EXPERT_GATING_FUNC,          hparams.expert_gating_func, uint32_t(LLAMA_EXPERT_GATING_FUNC_TYPE_SIGMOID));
+                ml.get_key(LLM_KV_EXPERT_GATING_FUNC,          hparams.expert_gating_func, false);
+                if (hparams.expert_gating_func == LLAMA_EXPERT_GATING_FUNC_TYPE_NONE) {
+                    hparams.expert_gating_func = LLAMA_EXPERT_GATING_FUNC_TYPE_SIGMOID;
+                }
 
                 switch (hparams.n_layer) {
                     case 46: type = LLM_TYPE_12B; break;  // GLM-4.5-Air