/model is not appear in cli v1.0.81

Describe the bug

After I update VScode to v1.135.0, I don't see /model anymore in copilot cli in BYOK mode.
What I did:
set environment value:

$env:COPILOT_PROVIDER_BASE_URL = "https:///v1"
$env:COPILOT_MODEL = "glm-5.3"
$env:COPILOT_EFFORTLEVEL = "high"
$env:COPILOT_PROVIDER_API_KEY = "sk-j"
$env:COPILOT_PROVIDER_MAX_PROMPT_TOKENS = "960000"
$env:COPILOT_PROVIDER_MAX_OUTPUT_TOKENS = "32000"
copilot

When I want to change to the other model in same provider, the /model is not appear any more.

Affected version

No response

Steps to reproduce the behavior

1. enabel venv

2. set env value
   $env:COPILOT_PROVIDER_BASE_URL = "https:///v1"
   $env:COPILOT_MODEL = "glm-5.3"
   $env:COPILOT_EFFORTLEVEL = "high"
   $env:COPILOT_PROVIDER_API_KEY = "sk-j"
   $env:COPILOT_PROVIDER_MAX_PROMPT_TOKENS = "960000"
   $env:COPILOT_PROVIDER_MAX_OUTPUT_TOKENS = "32000"

3. call /model

Expected behavior

No response

Additional context

No response

使用列出的 PowerShell 环境变量和 /model 命令，在 Copilot CLI v1.0.81 中复现该问题。首先跟踪 CLI 的 BYOK 模型选择或模型发现入口；当 /model 可用并允许在同一提供商的模型之间切换时，即表示完成。