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.

Start with the `/after` command and reproduce the one-time scheduling case using a task that is not ready when it runs. Trace what happens when Copilot defers the action to the next tick; done means a one-time prompt either schedules a later tick or keeps monitoring until the requested action executes.

Scritto dal modello di indicizzazione a partire dal testo della issue.