Action is not executed with `/after`: Copilot treats defers action until the next tick, which does not exist

### Describe the bug

I scheduled a one-time prompt with something like `/after 10m start evals every 100 steps for XYZ train job`. Copilot (in my case GPT-5.4 long context medium thinking) executed the task, but the train job wasn't ready enough to launch evals, so it deferred launching until the next schedule tick. However, since `/after` is a one-time prompt, there won't be another schedule tick; the action I wanted didn't execute. Unfortunately, I can't share the exact prompt or repo I used since they're internal.

### Affected version

GitHub Copilot CLI 1.0.61

### Steps to reproduce the behavior

1. Schedule a prompt with `/after` for a task that won't be ready to act on when the task is executed.
2. Copilot decides to act on the task "in the next tick" but not execute the action.

### Expected behavior

Copilot schedules another later tick to fulfill its promise, or monitors until the right time to execute the action.

### Additional context

Windows 11 x86_64, zsh inside zellij through WSL2 on windows terminal. GPT-5.4 medium thinking long context.

從 `/after` 命令開始，並使用一個在執行時尚未就緒的任務重現一次性排程案例。追蹤 Copilot 將動作延後到下一個 tick 時發生的情況；完成的條件是：一次性提示要麼排程較晚的 tick，要麼持續監控，直到要求的動作執行。

由索引模型根據 Issue 內容生成。