/mcp search fails with 400 Bad Request in every repo with a non-GitHub (Azure DevOps) git remote

Describe the bug

/mcp search (interactive MCP registry browser) consistently fails with:

Failed to load registry: Error: Failed to fetch MCP registry policy: 400 Bad Request

whenever Copilot CLI is started inside a trusted folder whose git remote points to Azure DevOps (dev.azure.com) instead of a GitHub-hosted remote. This affects our entire engineering org, since 100% of our repositories are hosted on Azure DevOps.

Environment

• Enterprise: GitHub Enterprise Cloud with data residency / EMU tenant
• OS: Windows
• Enterprise MCP Registry: configured and verified working (Azure API Center-backed registry, "Registry only" policy) — confirmed via direct curl calls that the registry itself returns HTTP 200 with the expected servers.

Workaround: Run /mcp search from a non-git folder to add servers once; they then work from any repo afterward via the persisted ~/.copilot/mcp-config.json.

Affected version

GitHub Copilot CLI 1.0.78

Steps to reproduce the behavior

1. Configure an enterprise MCP Registry URL + "Registry only" policy (per GitHub docs).
2. cd into any local git repository whose origin remote is an Azure DevOps URL (e.g. https://org@dev.azure.com/org/project/_git/repo).
3. Start copilot.
4. Run /mcp search.
5. Observe: Failed to load registry: Error: Failed to fetch MCP registry policy: 400 Bad Request.
6. cd outside any git repository (e.g. home directory) and start a fresh copilot process.
7. Run /mcp search again → succeeds, returns all registry servers.

Expected behavior

/mcp search should successfully fetch the registry policy regardless of the git remote host of the current working directory, or at minimum should not derive repo/org context from non-GitHub git remotes in a way that breaks the request.

Additional context

• The failure is tied to process startup cwd/git-remote context, not conversation state: /new inside the same running process does not recover it — only a full process relaunch outside a git-remote folder works.
• Once servers are added via the workaround below (outside a repo), they persist in ~/.copilot/mcp-config.json and connect fine from inside our Azure DevOps repos afterward — so the registry policy fetch specifically is what's broken, not general MCP connectivity.
• Reproduces consistently; not a timing/cache issue; not related to our enterprise's registry configuration (independently verified correct).

首先，在具有 Azure DevOps remote 的存储库中以及非 git 文件夹中复现 /mcp search，然后跟踪用于获取 MCP registry policy 的启动上下文。当无论当前 git remote 如何，registry 搜索都能成功，且不会破坏 ~/.copilot/mcp-config.json 中现有的持久化配置时，该 issue 即完成。