fix: 保留 Agent token 估算数值

- src/agent/agent-invocation.repository.ts: 脱敏 Agent 调用输入时保留 tokenEstimate 数字，避免 Prisma 写入失败

src/agent/agent-invocation.repository.ts

@@ -139,7 +139,15 @@ export class AgentInvocationRepository {
   private sanitizeInput(
     input: CreateAgentInvocationRecordInput,
   ): CreateAgentInvocationRecordInput {
-    return redactSensitive(input);
+    const redacted = redactSensitive({
+      ...input,
+      tokenEstimate: undefined,
+    });
+
+    return {
+      ...redacted,
+      tokenEstimate: input.tokenEstimate,
+    };
   }
 
   private inputDigest(