fix: Gemini 适配器补全 usage 字段映射 (#1233)

* fix: Gemini 适配器补全 usage 字段映射

Gemini API 的 usageMetadata 包含 cachedContentTokenCount 字段，
但此前未映射到 Anthropic 格式的 cache_read_input_tokens，导致
cache_creation_input_tokens 和 cache_read_input_tokens 始终为 0。

同时 message_delta 事件此前只携带 output_tokens，缺失
input_tokens、cache_creation_input_tokens、cache_read_input_tokens，
导致下游从 message_delta 读取最终 token 计数时获取不完整数据。

修复：
- 新增 cachedContentTokenCount → cache_read_input_tokens 映射
- message_start 和 message_delta 携带完整四个 usage 字段
- cache_creation_input_tokens 保持为 0（Gemini API 无等价概念）

Co-Authored-By: deepseek-v4-pro[1m] <deepseek-ai@claude-code-best.win>

* fix: 添加 cachedContentTokenCount 到 GeminiUsageMetadata 类型

streamAdapter.ts 使用 usage.cachedContentTokenCount 但该字段未
在 GeminiUsageMetadata 类型中声明。CodeRabbit 审查发现此问题。

Co-Authored-By: deepseek-v4-pro[1m] <deepseek-ai@claude-code-best.win>

---------

Co-authored-by: deepseek-v4-pro[1m] <deepseek-ai@claude-code-best.win>

packages/@ant/model-provider/src/providers/gemini/streamAdapter.ts

@@ -16,6 +16,7 @@ export async function* adaptGeminiStreamToAnthropic(
   let finishReason: string | undefined
   let inputTokens = 0
   let outputTokens = 0
+  let cachedReadTokens = 0
 
   for await (const chunk of stream) {
     const usage = chunk.usageMetadata
@@ -23,6 +24,7 @@ export async function* adaptGeminiStreamToAnthropic(
       inputTokens = usage.promptTokenCount ?? inputTokens
       outputTokens =
         (usage.candidatesTokenCount ?? 0) + (usage.thoughtsTokenCount ?? 0)
+      cachedReadTokens = usage.cachedContentTokenCount ?? cachedReadTokens
     }
 
     if (!started) {
@@ -41,7 +43,7 @@ export async function* adaptGeminiStreamToAnthropic(
             input_tokens: inputTokens,
             output_tokens: 0,
             cache_creation_input_tokens: 0,
-            cache_read_input_tokens: 0,
+            cache_read_input_tokens: cachedReadTokens,
           },
         },
       } as unknown as BetaRawMessageStreamEvent
@@ -204,7 +206,10 @@ export async function* adaptGeminiStreamToAnthropic(
         stop_sequence: null,
       },
       usage: {
+        input_tokens: inputTokens,
         output_tokens: outputTokens,
+        cache_creation_input_tokens: 0,
+        cache_read_input_tokens: cachedReadTokens,
       },
     } as BetaRawMessageStreamEvent
 

packages/@ant/model-provider/src/providers/gemini/types.ts

@@ -68,6 +68,7 @@ export type GeminiUsageMetadata = {
   candidatesTokenCount?: number
   thoughtsTokenCount?: number
   totalTokenCount?: number
+  cachedContentTokenCount?: number
 }
 
 export type GeminiCandidate = {