feat: unify MCP tool execution and chat callbacks

dap-gateway/src/main/java/io/shinhanlife/dap/mcg/presentation/ChatController.java

@@ -75,9 +75,9 @@ public class ChatController {
                 }
             }
 
-            String selectedModel = request.getOrDefault("model", "gemini-flash-latest").trim();
+            String selectedModel = request.getOrDefault("model", "cohere/north-mini-code:free").trim();
             if (selectedModel.isEmpty()) {
-                selectedModel = "gemini-flash-latest";
+                selectedModel = "cohere/north-mini-code:free";
             }
 
             // 1. gemini-flash-latest 선택 시 OpenRouter의 Google Gemma 4 모델로 라우팅
@@ -93,7 +93,7 @@ public class ChatController {
 
             Flux<String> responseStream = activeChatClient.prompt()
                     .user(message)
-                    .tools((Object[]) callbacks.toArray(new ToolCallback[0])) // Spring AI 2.0 uses tools()
+                    .toolCallbacks(callbacks.toArray(new ToolCallback[0]))
                     .options(org.springframework.ai.openai.OpenAiChatOptions.builder()
                             .model(selectedModel).build())
                     .stream()

dap-gateway/src/main/resources/application.yml

@@ -13,8 +13,9 @@ spring:
       api-key: ${OPENROUTER_API_KEY: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}
       base-url: https://openrouter.ai/api/v1
       chat:
+        completions-path: /chat/completions
         options:
-          model: google/gemma-4-31b-it:free
+          model: cohere/north-mini-code:free
           temperature: 0.3
 
 server:

dap-gateway/src/main/resources/static/chat.html

@@ -85,11 +85,11 @@
             </div>
             <div class="flex items-center gap-4">
                 <select id="model-select" class="bg-[#1e2128] text-slate-300 text-xs px-3 py-1.5 rounded-lg border border-white/10 focus:outline-none focus:border-emerald-500/50 cursor-pointer">
-                    <option value="inclusionai/ling-3.0-flash:free" selected>Ling 3.0 Flash ⭐ (기본 - OpenRouter)</option>
+                    <option value="inclusionai/ling-3.0-flash:free">Ling 3.0 Flash (무료 - 현재 제공 상태에 따라 제한될 수 있음)</option>
                     <option value="openai/gpt-oss-20b:free">GPT-OSS 20B (무료 - OpenRouter)</option>
                     <option value="google/gemma-4-31b-it:free">Gemma 4 31B (무료 - OpenRouter)</option>
                     <option value="nvidia/nemotron-3-nano-30b-a3b:free">NVIDIA Nemotron Nano 30B (무료 - OpenRouter)</option>
-                    <option value="cohere/north-mini-code:free">Cohere North Mini (무료 - OpenRouter)</option>
+                    <option value="cohere/north-mini-code:free" selected>Cohere North Mini (기본 · 무료 - OpenRouter)</option>
                     <option value="gemini-flash-latest">Gemini 1.5 Flash (직접 API - Google)</option>
                 </select>