fix: AI 对话解析多模型 JSON 配置，取 defaultModelId

兼容 apiSecret 纯模型名与 {defaultModelId,models} 结构，避免多模型配置后请求失败。

Co-authored-by: Cursor <cursoragent@cursor.com>

src/Oms.Application/Shared/AiLlmClient.cs

@@ -80,7 +80,11 @@ public class AiLlmClient
             throw new BusinessException($"请先配置 {provider.DisplayName} 的 API Key");
         }
 
-        var model = modelOverride ?? provider.ApiSecretEnc;
+        var model = modelOverride;
+        if (string.IsNullOrWhiteSpace(model))
+        {
+            model = ResolveConfiguredModelId(provider.ApiSecretEnc);
+        }
         if (string.IsNullOrWhiteSpace(model))
         {
             model = DefaultModelForProviderType(provider.ProviderType);
@@ -273,6 +277,84 @@ public class AiLlmClient
             "zhipu" => "glm-5.1",
             _ => null
         };
+
+    /// <summary>
+    /// 解析 ApiSecret：兼容纯模型名，或多模型 JSON
+    /// {"defaultModelId":"...","models":[{"modelId":"...","role":"文字"}]}。
+    /// </summary>
+    private static string? ResolveConfiguredModelId(string? apiSecret)
+    {
+        var secret = (apiSecret ?? string.Empty).Trim();
+        if (string.IsNullOrWhiteSpace(secret))
+        {
+            return null;
+        }
+
+        if (!secret.StartsWith('{'))
+        {
+            return secret;
+        }
+
+        try
+        {
+            using var doc = JsonDocument.Parse(secret);
+            var root = doc.RootElement;
+            if (root.TryGetProperty("defaultModelId", out var defaultModel) &&
+                defaultModel.ValueKind == JsonValueKind.String)
+            {
+                var id = defaultModel.GetString()?.Trim();
+                if (!string.IsNullOrWhiteSpace(id))
+                {
+                    return id;
+                }
+            }
+
+            if (root.TryGetProperty("models", out var models) &&
+                models.ValueKind == JsonValueKind.Array)
+            {
+                foreach (var item in models.EnumerateArray())
+                {
+                    if (!item.TryGetProperty("modelId", out var modelIdEl) ||
+                        modelIdEl.ValueKind != JsonValueKind.String)
+                    {
+                        continue;
+                    }
+
+                    var modelId = modelIdEl.GetString()?.Trim();
+                    if (string.IsNullOrWhiteSpace(modelId))
+                    {
+                        continue;
+                    }
+
+                    if (item.TryGetProperty("role", out var roleEl) &&
+                        roleEl.ValueKind == JsonValueKind.String &&
+                        string.Equals(roleEl.GetString(), "文字", StringComparison.Ordinal))
+                    {
+                        return modelId;
+                    }
+                }
+
+                foreach (var item in models.EnumerateArray())
+                {
+                    if (item.TryGetProperty("modelId", out var modelIdEl) &&
+                        modelIdEl.ValueKind == JsonValueKind.String)
+                    {
+                        var modelId = modelIdEl.GetString()?.Trim();
+                        if (!string.IsNullOrWhiteSpace(modelId))
+                        {
+                            return modelId;
+                        }
+                    }
+                }
+            }
+        }
+        catch (JsonException)
+        {
+            return secret;
+        }
+
+        return null;
+    }
 }
 
 public static class AiLlmServiceExtensions