Claude Opus 4.6 (high) returns "model not supported" error after being told to wait for quota reset on GitHub Copilot Pro+

**Description**
After being prompted by the CLI to wait until a specific time before using Claude Opus 4.6 (high)
due to quota limits, I waited as instructed. Upon retrying, I now receive the following error:

Execution failed: CAPIError: 400 The requested model is not supported.
(Request ID: 49DD:6BE68:13F49D2:16EC696:69E6DD3C)

**Actual Behavior**
Error: CAPIError: 400 The requested model is not supported

**Environment**
- Plan: GitHub Copilot Pro+
- CLI Version: GitHub Copilot CLI 1.0.32
- OS: Windows

**Notes**
The error message is misleading -- it says "model not supported" rather than a quota or
availability issue, making it hard to diagnose.

### Affected version

GitHub Copilot CLI 1.0.32 onwards

### Steps to reproduce the behavior

**Steps to Reproduce**
1. Select Claude Opus 4.6 (high) via `/model` in Copilot CLI
2. Hit quota limit -- CLI prompts to wait until a specific time
3. Wait until the indicated time has passed
4. Try again -- error occurs

### Expected behavior

**Expected Behavior**
The model should be accessible after the quota reset window.

### Additional context

_No response_

從 Windows 上的 GitHub Copilot CLI 1.0.32 中的 `/model` 流程開始，並在指示的 quota reset 後重現該故障。追蹤針對 Claude Opus 4.6 (high) 的請求，並將回報的回應與 quota 或 availability 狀態進行比較。完成標準是模型在 reset 後能夠正常運作，或錯誤明確指出實際限制。

由索引模型根據 Issue 內容生成。