llama : re-enable manual LoRA adapter free (#19983)

* Re-enable manual LoRA adapter free

* Remove stale "all adapters must be loaded before context creation" stale comments

src/llama-adapter.h

@@ -61,6 +61,8 @@ struct llama_adapter_lora_weight {
 };
 
 struct llama_adapter_lora {
+    llama_model * model = nullptr;
+
     // map tensor name to lora_a_b
     std::unordered_map<std::string, llama_adapter_lora_weight> ab_map;
 
@@ -75,7 +77,7 @@ struct llama_adapter_lora {
     // activated lora (aLoRA)
     std::vector<llama_token> alora_invocation_tokens;
 
-    llama_adapter_lora() = default;
+    explicit llama_adapter_lora(llama_model * model) : model(model) {}
     ~llama_adapter_lora() = default;
 
     llama_adapter_lora_weight * get_weight(ggml_tensor * w);