feat: add AI endpoint manager plugin with configuration and routing capabilities

- Introduced `ai_endpoint_mgr` plugin to manage multiple AI provider endpoints.
- Added configuration reference documentation for `config.toml`.
- Implemented endpoint loading, active endpoint switching, and model mutation.
- Included error handling for missing endpoints and configuration failures.
- Developed unit tests covering various scenarios including error paths and concurrency.

dstalk_gui/src/main.cpp

@@ -27,6 +27,7 @@
 // 在启动时从主机查询获取的服务 vtable 全局指针。
 static const dstalk_ai_service_t*      g_ai_svc  = nullptr;
 static const dstalk_session_service_t* g_session_svc = nullptr;
+static const dstalk_ai_endpoint_mgr_t* g_endpoint_mgr = nullptr;  // I08: AI endpoint manager（可选）/ optional
 
 // ---- 常量 / Constants ----
 
@@ -287,10 +288,19 @@ static void renderStatusBar(AppContext& ctx) {
     }
 
     // 状态文本：模型名 | 消息条数 | 流式状态 / Status text: model name | message count | streaming state
+    // I08: 添加 endpoint manager 信息（如果可用）/ add endpoint manager info (if available)
     char buf[256];
-    snprintf(buf, sizeof(buf), "%s | %d messages | %s",
-             gs.model_name.c_str(), msgCount,
-             gs.streaming ? "streaming" : "ready");
+    const char* active_ep = nullptr;
+    if (g_endpoint_mgr) active_ep = g_endpoint_mgr->get_active();
+    if (active_ep && active_ep[0]) {
+        snprintf(buf, sizeof(buf), "%s | %d messages | %s | ep:%s",
+                 gs.model_name.c_str(), msgCount,
+                 gs.streaming ? "streaming" : "ready", active_ep);
+    } else {
+        snprintf(buf, sizeof(buf), "%s | %d messages | %s",
+                 gs.model_name.c_str(), msgCount,
+                 gs.streaming ? "streaming" : "ready");
+    }
     drawText(r, static_cast<float>(PADDING),
              barY + (STATUS_H - CHAR_H) / 2.0f, buf, COL_WHITE);
 }
@@ -832,6 +842,9 @@ int main(int argc, char* argv[]) {
     if (!ai_provider) ai_provider = "ai_openai";
     g_ai_svc      = static_cast<const dstalk_ai_service_t*>(dstalk_service_query(ai_provider, 1));
     g_session_svc = static_cast<const dstalk_session_service_t*>(dstalk_service_query("session", 1));
+    // I08: 查询 AI endpoint manager（可选服务）/ query AI endpoint manager (optional service)
+    g_endpoint_mgr = static_cast<const dstalk_ai_endpoint_mgr_t*>(
+                         dstalk_service_query("ai_endpoint_mgr", 1));
     if (!g_ai_svc)      dstalk_log(3, "AI service not found (check plugins directory)");
     if (!g_session_svc) dstalk_log(3, "Session service not found");
 
@@ -899,15 +912,25 @@ int main(int argc, char* argv[]) {
                 std::string& userMsg =
                     ctx.state.messages[ctx.state.messages.size() - 2].content;
                 int rc = -1;
-                if (g_ai_svc) {
+                // I08: 优先通过 endpoint_mgr 路由，fallback 到 g_ai_svc / prefer endpoint_mgr, fallback to g_ai_svc
+                const bool use_mgr = (g_endpoint_mgr && g_endpoint_mgr->count() > 0);
+                if (use_mgr || g_ai_svc) {
                     int hcount = 0;
                     const dstalk_message_t* history = g_session_svc
                         ? g_session_svc->history(&hcount) : nullptr;
-                    dstalk_chat_result_t result = g_ai_svc->chat_stream(
-                        history, hcount, userMsg.c_str(),
-                        streamTokenCallback, &ctx);
+                    dstalk_chat_result_t result;
+                    if (use_mgr) {
+                        result = g_endpoint_mgr->chat_stream(
+                            nullptr, history, hcount, userMsg.c_str(),
+                            streamTokenCallback, &ctx);
+                    } else {
+                        result = g_ai_svc->chat_stream(
+                            history, hcount, userMsg.c_str(),
+                            streamTokenCallback, &ctx);
+                    }
                     rc = result.ok ? 0 : -1;
-                    g_ai_svc->free_result(&result);
+                    if (use_mgr) g_endpoint_mgr->free_result(&result);
+                    else         g_ai_svc->free_result(&result);
                 }
 
                 // 流式传输完成（或被取消）