Restarting copilot uses AI credits

### Describe the bug

Since a while now using `/restart` or `/resume` (also `/update`) consumes non trivial amount of AI credits.

According to my experience there seem to be a somehow fixed amount of 174 AI credits being consumed (not sure where this number comes from). According to https://docs.github.com/de/copilot/concepts/billing/usage-based-billing-for-individuals an AI credit costs 0.01 $ resulting in an amount of 1,74 $ charged for ... nothing!

### Affected version

_No response_

### Steps to reproduce the behavior

- Do some work in copilot cli
- Use `/restart`
- Exit copilot without doing anything
- You see the session used 174 AI credits even though not a single prompt was submitted

### Expected behavior

I can restart/resume without getting charged until actually work is performed!

### Additional context

_No response_

Start by tracing the /restart, /resume, and /update command paths in the Copilot CLI and compare them with the billing or credit-usage path. Reproduce the reported session with no prompt, then verify that restarting or resuming consumes no AI credits while normal prompt usage remains accounted for.

索引モデルが issue の本文から書いたものです。