实现listExperiments端点和通用转发机制

- 添加forwardToCodeAssist通用转发函数支持简单端点
- 添加handleSimpleEndpoint通用路由处理函数
- 注册listExperiments路由(v1internal和v1beta)
- 解决gemini-cli启动时404 Not Found错误

src/services/geminiAccountService.js

@@ -1060,6 +1060,47 @@ async function getOauthClient(accessToken, refreshToken, proxyConfig = null) {
   return client
 }
 
+// 通用的 Code Assist API 转发函数（用于简单的请求/响应端点）
+// 适用于：loadCodeAssist, onboardUser, countTokens, listExperiments 等不需要特殊处理的端点
+async function forwardToCodeAssist(client, apiMethod, requestBody, proxyConfig = null) {
+  const axios = require('axios')
+  const CODE_ASSIST_ENDPOINT = 'https://cloudcode-pa.googleapis.com'
+  const CODE_ASSIST_API_VERSION = 'v1internal'
+
+  const { token } = await client.getAccessToken()
+  const proxyAgent = ProxyHelper.createProxyAgent(proxyConfig)
+
+  logger.info(`📡 ${apiMethod} API调用开始`)
+
+  const axiosConfig = {
+    url: `${CODE_ASSIST_ENDPOINT}/${CODE_ASSIST_API_VERSION}:${apiMethod}`,
+    method: 'POST',
+    headers: {
+      Authorization: `Bearer ${token}`,
+      'Content-Type': 'application/json'
+    },
+    data: requestBody,
+    timeout: 30000
+  }
+
+  // 添加代理配置
+  if (proxyAgent) {
+    axiosConfig.httpAgent = proxyAgent
+    axiosConfig.httpsAgent = proxyAgent
+    axiosConfig.proxy = false
+    logger.info(
+      `🌐 Using proxy for ${apiMethod}: ${ProxyHelper.getProxyDescription(proxyConfig)}`
+    )
+  } else {
+    logger.debug(`🌐 No proxy configured for ${apiMethod}`)
+  }
+
+  const response = await axios(axiosConfig)
+
+  logger.info(`✅ ${apiMethod} API调用成功`)
+  return response.data
+}
+
 // 调用 Google Code Assist API 的 loadCodeAssist 方法（支持代理）
 async function loadCodeAssist(client, projectId = null, proxyConfig = null) {
   const axios = require('axios')
@@ -1529,6 +1570,7 @@ module.exports = {
   getAccountRateLimitInfo,
   isTokenExpired,
   getOauthClient,
+  forwardToCodeAssist, // 通用转发函数
   loadCodeAssist,
   getOnboardTier,
   onboardUser,