[Bug] Unexpected triple point deduction when multiple sessions are active via /resume

### Describe the bug

Issue Body (内容)
Describe the bug
When multiple Copilot CLI windows are open and running resumed sessions, submitting a prompt in only one of the windows results in an unexpected multiple point deduction. Closing the background windows resolves the issue.

Steps to Reproduce

Open multiple Copilot CLI windows simultaneously.

Use the /resume command to restore 5 frequently used sessions across these windows.

Ensure a 1x cost model is selected.

Submit a question in only 1 of the active sessions.

Check the point/quota deduction.

Actual Behavior
A single question deducts 3 points from the quota, even though a 1x model is being used.

Expected Behavior
The question should only deduct 1 point, regardless of how many other inactive CLI windows or sessions are open in the background.

Additional Context / Workaround
Closing the other Copilot CLI windows immediately resolves the issue, and subsequent questions correctly return to deducting only 1 point.

### Affected version

 v1.0.24

### Steps to reproduce the behavior

_No response_

### Expected behavior

_No response_

### Additional context

_No response_

まず、説明されているとおり、複数の Copilot CLI ウィンドウ、再開したセッション、1x コストモデルを使って問題を再現します。1 つのセッションがプロンプトを送信する際に、他のウィンドウが開いている場合と閉じている場合で、クォータの差し引きを比較します。非アクティブなバックグラウンドセッションに関係なく、1 つのプロンプトで 1 ポイントだけ差し引かれれば完了です。

索引モデルが issue の本文から書いたものです。