Feature Request: /remote should support non-GitHub git repositories (e.g. GitLab, Bitbucket)

## Problem
`/remote` fails with `Remote session disabled: not in a GitHub repository` when used in a GitLab (or other) repository.

## Proposed Solution
The remote session feature should work independently of the git host — session control via GitHub account, regardless of where the code is hosted.

## Use Case
Teams using GitLab want to use /remote to control their Copilot CLI session from GitHub web/mobile, but are blocked by the repository host check.

## Additional Context
The CLI is already authenticated via GitHub, so the restriction to GitHub-hosted repos feels unnecessary for the remote control functionality itself.

在 CLI 中搜尋確切的錯誤訊息和 /remote 命令，然後追蹤 repository 主機檢查及其測試。確認 GitHub 驗證如何控制遠端工作階段，並將完成標準定義為：允許 GitLab 或其他 Git repository，同時不破壞現有的 GitHub 託管流程。

由索引模型根據 Issue 內容生成。