[bug]copilot-cli bug report: One prompt triggered autopilot mode infinite loop

### Describe the bug

After completing a simple task, copilot is unable to stop itself, continuous loop trying to call a "task_complete" tool which does not exist，it used up all my credit limit at once.

### Affected version

_No response_

### Steps to reproduce the behavior

_No response_

### Expected behavior

_No response_

### Additional context

_No response_

Start by reproducing the reported autopilot-mode loop in copilot-cli, using the screenshots and the repeated "task_complete" tool call as the failure clues. Trace the autopilot completion path and verify that a simple completed task stops without repeatedly invoking a nonexistent tool or consuming further credits.

索引モデルが issue の本文から書いたものです。