feat(loop): agent loop（8 轮 + checkpoint + 流式 + 记忆注入/提取 + trace + 工具超时回喂）

internal/runtime/loop/checkpoint.go

@@ -0,0 +1,46 @@
+package loop
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+
+	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/model"
+	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/persist"
+)
+
+// checkpointState is the durable snapshot persisted at every step. Carrying the
+// message window and the step index lets a long-running task be resumed from the
+// latest checkpoint without losing context (design §1 durable execution).
+type checkpointState struct {
+	Step       int             `json:"step"`
+	Messages   []model.Message `json:"messages"`
+	StopReason string          `json:"stop_reason,omitempty"`
+}
+
+// saveCheckpoint persists a snapshot at step. It never fails the run: a nil store
+// is a no-op and a marshal/save error is logged.
+func (l *Loop) saveCheckpoint(ctx context.Context, sessionID string, step int, messages []model.Message, stopReason string) {
+	if l.checkpoint == nil {
+		return
+	}
+	state := checkpointState{
+		Step:       step,
+		Messages:   messages,
+		StopReason: stopReason,
+	}
+	buf, err := json.Marshal(state)
+	if err != nil {
+		l.log.Warn("checkpoint marshal", "step", step, "error", err)
+		return
+	}
+	cp := &persist.Checkpoint{
+		ID:      fmt.Sprintf("%s:%d", sessionID, step),
+		AgentID: sessionID,
+		Step:    step,
+		State:   buf,
+	}
+	if err := l.checkpoint.Save(ctx, cp); err != nil {
+		l.log.Warn("checkpoint save", "step", step, "error", err)
+	}
+}