[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_

首先按照描述，使用多個 Copilot CLI 視窗、已恢復的工作階段和 1x 成本模型重現此問題。比較一個工作階段提交 prompt 時，其他視窗處於開啟與關閉狀態下的配額扣除情況。當無論存在多少不活躍的背景工作階段，一個 prompt 都只扣除 1 點時，即視為完成。

由索引模型根據 Issue 內容生成。