fix: 修复非 Anthropic provider 署名模型名获取错误

getRealModelName() 现在会检查 provider 特定环境变量（OPENAI_MODEL、GEMINI_MODEL、GROK_MODEL），
确保通过这些变量设置模型时署名显示真实名称而非 Anthropic 默认模型名。

Co-Authored-By: opus[1m] <noreply@anthropic.com>

src/utils/attributionModel.ts

@@ -0,0 +1,31 @@
+import {
+  getMainLoopModel,
+  getUserSpecifiedModelSetting,
+} from './model/model.js'
+import { getAPIProvider } from './model/providers.js'
+
+function getProviderModelEnv(): string | undefined {
+  const provider = getAPIProvider()
+  switch (provider) {
+    case 'openai':
+      return process.env.OPENAI_MODEL
+    case 'gemini':
+      return process.env.GEMINI_MODEL
+    case 'grok':
+      return process.env.GROK_MODEL
+    default:
+      return undefined
+  }
+}
+
+export function getRealModelName(): string {
+  const userSetting = getUserSpecifiedModelSetting()
+  if (userSetting !== undefined && userSetting !== null) {
+    return userSetting
+  }
+  const providerModel = getProviderModelEnv()
+  if (providerModel) {
+    return providerModel
+  }
+  return getMainLoopModel()
+}