High CPU usage in copilot-cli

### Describe the bug

When I run copilot cli, it's taking 100% of one of the CPUs, even though the only thing the copilot is doing is waiting for a sleep operation..

```
Shell Wait then recheck CI status
sleep 550; cd /home/matste/ [...]
```

```
PID USER PRI NI VIRT RES SHR S CPU%▽MEM% TIME+ Command
38098 matste 20 0 15.9G 726M 149M S 27.2 2.8 0:47.95 copilot
```

### Affected version

GitHub Copilot CLI 1.0.78.

### Steps to reproduce the behavior

Ask copilot to execute any command.

### Expected behavior

How hard is it to implement a text-only program that doesn't do active waiting?

### Additional context

_No response_

Start by reproducing the issue in GitHub Copilot CLI 1.0.78 with a command such as `sleep 550`, then inspect the command-waiting path. Done means the CLI remains responsive but no longer consumes a CPU while waiting; verify the result with the same process monitor and reproduction command.

Written by the indexing model from the issue text.