Desktop app routes public github.com issue links to enterprise host instead of preserving origin

> *This was generated by AI during triage.*

## Summary

Opening a public `github.com` issue link in the desktop app creates an inline tab that fails with:

> We couldn't load this issue. Please try again.

The tab offers only **Retry**. Logs show the request being sent to the active enterprise API host instead of `api.github.com`.

## Environment

- GitHub Copilot desktop app v1.0.25
- App-spawned Copilot CLI v1.0.71
- Windows 11
- Active/default account belongs to an enterprise GitHub host
- `github.com` access is also configured

## Reproduction

1. Open this public issue link in the desktop app:
https://github.com/github/copilot-cli/issues/4176
2. Allow the app to open it as an inline issue tab.
3. Observe the loading failure and **Retry** button.

Older public issues, including #2901, produced the same failure, ruling out new-issue propagation as the explanation.

## Expected behavior

The link's origin host should be preserved. The app should either:

- load the `github.com` issue inline using `github.com`; or
- explain that inline loading is unsupported and offer **Open in browser**.

An `owner/repository/number` resource must not be resolved against a different GitHub host.

## Sanitized evidence

```text
04:54:14.701589Z subscribe_resource owner=github repo=copilot-cli number=4176 [no host]
04:54:28.055442Z get_issue owner=github repo=copilot-cli number=4176 [no host]
04:54:28.143159Z API request failed status=404
https:///api/v3/repos/github/copilot-cli/issues/4176
```

- The failed tab generated 36 equivalent enterprise-host 404 responses.
- The active app log contained no `api.github.com` request.
- Nine older public `github.com` issues failed through the same enterprise endpoint.
- Failures reported `auth_required=false` and `rate_limited=false`.

## Observed versus unconfirmed

**Observed:** public `github.com` issue resources are routed to the active enterprise API host, and the failed inline view provides no browser fallback.

**Unconfirmed:** logs do not contain the original clicked URL, so they do not show where its `github.com` host was lost. Pull-request behavior has not been verified.

## Related issue

Related, but not a duplicate: [#4148](https://github.com/github/copilot-cli/issues/4148).

## Questions

1. Where should the source host enter the inline resource identity?
2. Does inline loading support resources from multiple GitHub hosts?
3. Can failed or unsupported inline loads offer **Open in browser**?

## Additional context

This was a read-only investigation. A sanitized screenshot is available showing the inline error and its **Retry**-only recovery.

首先使用提供的重現步驟和已清理的日誌，追蹤 inline issue 分頁以及 subscribe_resource/get_issue 路徑。檢查在 API 請求之前被點擊的 host 在哪裡遺失，接著驗證公開連結是否保留 github.com，或是否提供 Open in browser 備援選項，包括 Enterprise host 情境。

由索引模型根據 Issue 內容生成。