feat: support durable task cancellation without foreign keys

internal/storage/mysql/worker_cancellation.go

@@ -0,0 +1,35 @@
+package mysql
+
+import (
+	"context"
+	"database/sql"
+
+	"git.yuntuo.hk/k2safe/orbit/platform/auth"
+	"git.yuntuo.hk/k2safe/orbit/pulse/worker"
+)
+
+// Cancellations 读取当前有效会话持有的取消意图；断线后由新会话 Resume 和扫描重新交付。
+// 通知允许重复或迟到，不能代替任务结果；256 对应单 Worker 最大持久化容量。
+func (s *ExecutionStore) Cancellations(ctx context.Context, token auth.Token, b worker.Binding) ([]worker.Cancellation, error) {
+	out := []worker.Cancellation{}
+	err := s.transaction(ctx, token, "workers:consume", func(tx *sql.Tx, p auth.Permissions) error {
+		state, err := s.lockSession(ctx, tx, token, b, p)
+		if err != nil {
+			return err
+		}
+		rows, err := tx.QueryContext(ctx, `SELECT t.id,a.id,a.epoch,t.cancel_requested_at FROM pulse_attempts a JOIN pulse_tasks t ON t.namespace_id=a.namespace_id AND t.id=a.task_id AND t.current_attempt_id=a.id WHERE a.namespace_id=? AND a.session_id=? AND a.state='RUNNING' AND t.state='RUNNING' AND t.queue_id=? AND t.cancel_requested_at IS NOT NULL ORDER BY a.id LIMIT 256`, token.NamespaceID, b.SessionID, state.queue)
+		if err != nil {
+			return err
+		}
+		defer rows.Close()
+		for rows.Next() {
+			var c worker.Cancellation
+			if err := rows.Scan(&c.TaskID, &c.AttemptID, &c.Epoch, &c.RequestedAt); err != nil {
+				return err
+			}
+			out = append(out, c)
+		}
+		return rows.Err()
+	})
+	return out, err
+}