feat: langfuse tracing 增加 thinking 参数记录

在 recordLLMObservation 中添加 thinking 配置（type/budgetTokens），
所有 provider（claude/gemini/openai）及 tokenEstimation、sideQuery
调用处同步传递 thinking 信息，便于 Langfuse 面板观察 thinking 使用情况。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/services/langfuse/tracing.ts

@@ -78,6 +78,11 @@ export function recordLLMObservation(
     endTime?: Date
     completionStartTime?: Date
     tools?: unknown
+    /** Thinking depth configuration used for this request */
+    thinking?: {
+      type: string
+      budgetTokens?: number
+    }
   },
 ): void {
   if (!rootSpan || !isLangfuseEnabled()) return
@@ -97,6 +102,10 @@ export function recordLLMObservation(
         metadata: {
           provider: params.provider,
           model: params.model,
+          ...(params.thinking && { thinkingType: params.thinking.type }),
+          ...(params.thinking?.budgetTokens !== undefined && {
+            thinkingBudgetTokens: params.thinking.budgetTokens,
+          }),
         },
         ...(params.completionStartTime && { completionStartTime: params.completionStartTime }),
       },