perf: sync protocol and core hardening updates

internal/store/dispatch_outbox.go

@@ -2,11 +2,20 @@ package store
 
 import (
 	"context"
+	"errors"
 	"time"
 
 	"telesrv/internal/domain"
 )
 
+// ErrDispatchLeaseLost means a completion belongs to an older claim attempt.
+// Callers must not overwrite/delete the row now owned by a newer worker.
+var ErrDispatchLeaseLost = errors.New("dispatch outbox lease lost")
+
+// DispatchOutboxLogicalShards 是稳定的 user→lane 哈希空间。运行时 worker 数
+// 只能改变 shard 的归属，不能改变这个值；PG 表达式索引也固定使用 256。
+const DispatchOutboxLogicalShards = 256
+
 // DispatchOutboxItem 是待投递给在线 session 的 update 任务。
 type DispatchOutboxItem struct {
 	ID               int64
@@ -21,7 +30,7 @@ type DispatchOutboxItem struct {
 // DispatchOutboxStore 持久化 transactional outbox。
 type DispatchOutboxStore interface {
 	ClaimPending(ctx context.Context, limit int) ([]DispatchOutboxItem, error)
-	MarkDelivered(ctx context.Context, targetUserID, id int64) error
-	MarkFailed(ctx context.Context, targetUserID, id int64, lastError string) error
+	MarkDelivered(ctx context.Context, item DispatchOutboxItem) error
+	MarkFailed(ctx context.Context, item DispatchOutboxItem, lastError string) error
 	DeleteFailed(ctx context.Context, olderThan time.Duration, limit int) (int, error)
 }