model : support granite multilingual embeddings R2 (ibm-granite/granite-embedding-{97,311}m-multilingual-r2) (#22716)

* Add support for the ibm-granite/granite-embedding-{97m,311m}-multilingual-r2 embedding models:

* Added a version of the gpt4o tokenizer that has a fixed regex (better handling of marks), and different token merging setting for the 97m model
* Reused gemma4 tokenizer for the 311m model

* granite-embedding-*-multilingual-r2 : add support SwiGLU FFN for Granite Embedding Multilingual R2

* added new GGUF key <arch>.hidden_activation (LLM_KV_HIDDEN_ACT) + writer
* added a forward declaration of llm_ffn_op_type to llama-hparams.h
* added llm_ffn_op in hparams
* added LLM_FFN_NONE = 0 sentinel to llm_ffn_op_type (value-initialization), modern-bert: explicitly assigns LLM_FFN_GEGLU before reading GGUF (unchanged).
* centralized hidden_act mapping in llama-model.cpp, added llm_ffn_op_type_from_string() helper, mirroring rope_scaling_type/llama_rope_scaling_type_from_string()
* modern-bert reads the GGUF key (when present) and uses the resulting op in its FFN graph

* Added granite-embedding-{97m,311m}-multilingual-r2 to the converter code

* Added the hashes for the granite embedding multilingual R2 models
* Set the hidden_activation in the GGUF if the field is present in config.json (such as for the granite embedding models)

src/llama-model.cpp

@@ -822,6 +822,28 @@ static llama_rope_scaling_type llama_rope_scaling_type_from_string(const std::st
     return LLAMA_ROPE_SCALING_TYPE_UNSPECIFIED;
 }
 
+// Maps the GGUF `<arch>.hidden_activation` string to the FFN op type used by the
+// graph builders. Only gated activations that map cleanly to llm_ffn_op_type are
+// listed; unrecognized values fall back to GeGLU, which matches the historical
+// default for ModernBert-style architectures.
+static const std::map<std::string, llm_ffn_op_type> LLM_FFN_OP_TYPES_FROM_STRING = {
+    { "gelu",   LLM_FFN_GEGLU  },
+    { "geglu",  LLM_FFN_GEGLU  },
+    { "silu",   LLM_FFN_SWIGLU },
+    { "swish",  LLM_FFN_SWIGLU },
+    { "swiglu", LLM_FFN_SWIGLU },
+    { "relu",   LLM_FFN_RELU   },
+    { "reglu",  LLM_FFN_REGLU  },
+};
+
+llm_ffn_op_type llm_ffn_op_type_from_string(const std::string & name, llm_ffn_op_type fallback) {
+    const auto it = LLM_FFN_OP_TYPES_FROM_STRING.find(name);
+    if (it != LLM_FFN_OP_TYPES_FROM_STRING.end()) {
+        return it->second;
+    }
+    return fallback;
+}
+
 // CPU: ACCEL -> GPU host -> CPU extra -> CPU
 static buft_list_t make_cpu_buft_list(const std::vector<llama_device> & devices, bool use_extra_bufts, bool no_host) {
     buft_list_t buft_list;