Version: 0.9.75.dev.260505

后端：
1.收口阶段 6 agent 结构迁移，将 newAgent 内核与 agentsvc 编排层迁入 services/agent
- 切换 Agent 启动装配与 HTTP handler 直连 agent sv，移除旧 service agent bridge
- 补齐 Agent 对 memory、task、task-class、schedule 的 RPC 适配与契约字段
- 扩展 schedule、task、task-class RPC/contract 支撑 Agent 查询、写入与 provider 切流
- 更新迁移文档、README 与相关注释，明确 agent 当前切流点和剩余 memory 迁移面

backend/services/agent/stream/usage.go

@@ -0,0 +1,41 @@
+package agentstream
+
+import "github.com/cloudwego/eino/schema"
+
+// CloneUsage 深拷贝 TokenUsage。
+func CloneUsage(usage *schema.TokenUsage) *schema.TokenUsage {
+	if usage == nil {
+		return nil
+	}
+	copied := *usage
+	return &copied
+}
+
+// MergeUsage 合并两段 usage，取更大值。
+// 适用于同一次调用不同流分片的 usage 收敛。
+func MergeUsage(base *schema.TokenUsage, incoming *schema.TokenUsage) *schema.TokenUsage {
+	if incoming == nil {
+		return CloneUsage(base)
+	}
+	if base == nil {
+		return CloneUsage(incoming)
+	}
+
+	merged := *base
+	if incoming.PromptTokens > merged.PromptTokens {
+		merged.PromptTokens = incoming.PromptTokens
+	}
+	if incoming.CompletionTokens > merged.CompletionTokens {
+		merged.CompletionTokens = incoming.CompletionTokens
+	}
+	if incoming.TotalTokens > merged.TotalTokens {
+		merged.TotalTokens = incoming.TotalTokens
+	}
+	if incoming.PromptTokenDetails.CachedTokens > merged.PromptTokenDetails.CachedTokens {
+		merged.PromptTokenDetails.CachedTokens = incoming.PromptTokenDetails.CachedTokens
+	}
+	if incoming.CompletionTokensDetails.ReasoningTokens > merged.CompletionTokensDetails.ReasoningTokens {
+		merged.CompletionTokensDetails.ReasoningTokens = incoming.CompletionTokensDetails.ReasoningTokens
+	}
+	return &merged
+}