feat(antigravity): 增强网关功能和 thinking 块处理

主要改进：
- 优化 thinking blocks 过滤策略，支持 Auto 模式降级
- 将无效 thinking block 内容转为普通 text
- 保留单个空白 text block，不过滤
- 重构配额刷新机制，统一与 Claude 一致
- 支持 cachedContentTokenCount 映射到 cache_read_input_tokens
- Haiku 模型映射到 Sonnet
- 添加 /antigravity/v1/models 端点支持
- countTokens 端点直接返回空值

backend/internal/server/routes/gateway.go

@@ -13,8 +13,8 @@ import (
 func RegisterGatewayRoutes(
 	r *gin.Engine,
 	h *handler.Handlers,
-	apiKeyAuth middleware.APIKeyAuthMiddleware,
-	apiKeyService *service.APIKeyService,
+	apiKeyAuth middleware.ApiKeyAuthMiddleware,
+	apiKeyService *service.ApiKeyService,
 	subscriptionService *service.SubscriptionService,
 	cfg *config.Config,
 ) {
@@ -36,7 +36,7 @@ func RegisterGatewayRoutes(
 	// Gemini 原生 API 兼容层（Gemini SDK/CLI 直连）
 	gemini := r.Group("/v1beta")
 	gemini.Use(bodyLimit)
-	gemini.Use(middleware.APIKeyAuthWithSubscriptionGoogle(apiKeyService, subscriptionService, cfg))
+	gemini.Use(middleware.ApiKeyAuthWithSubscriptionGoogle(apiKeyService, subscriptionService, cfg))
 	{
 		gemini.GET("/models", h.Gateway.GeminiV1BetaListModels)
 		gemini.GET("/models/:model", h.Gateway.GeminiV1BetaGetModel)
@@ -47,6 +47,9 @@ func RegisterGatewayRoutes(
 	// OpenAI Responses API（不带v1前缀的别名）
 	r.POST("/responses", bodyLimit, gin.HandlerFunc(apiKeyAuth), h.OpenAIGateway.Responses)
 
+	// Antigravity 模型列表
+	r.GET("/antigravity/models", gin.HandlerFunc(apiKeyAuth), h.Gateway.AntigravityModels)
+
 	// Antigravity 专用路由（仅使用 antigravity 账户，不混合调度）
 	antigravityV1 := r.Group("/antigravity/v1")
 	antigravityV1.Use(bodyLimit)
@@ -55,14 +58,14 @@ func RegisterGatewayRoutes(
 	{
 		antigravityV1.POST("/messages", h.Gateway.Messages)
 		antigravityV1.POST("/messages/count_tokens", h.Gateway.CountTokens)
-		antigravityV1.GET("/models", h.Gateway.Models)
+		antigravityV1.GET("/models", h.Gateway.AntigravityModels)
 		antigravityV1.GET("/usage", h.Gateway.Usage)
 	}
 
 	antigravityV1Beta := r.Group("/antigravity/v1beta")
 	antigravityV1Beta.Use(bodyLimit)
 	antigravityV1Beta.Use(middleware.ForcePlatform(service.PlatformAntigravity))
-	antigravityV1Beta.Use(middleware.APIKeyAuthWithSubscriptionGoogle(apiKeyService, subscriptionService, cfg))
+	antigravityV1Beta.Use(middleware.ApiKeyAuthWithSubscriptionGoogle(apiKeyService, subscriptionService, cfg))
 	{
 		antigravityV1Beta.GET("/models", h.Gateway.GeminiV1BetaListModels)
 		antigravityV1Beta.GET("/models/:model", h.Gateway.GeminiV1BetaGetModel)