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.

Start by tracing the inline issue tab and subscribe_resource/get_issue path using the provided reproduction and sanitized logs. Check where the clicked host is lost before the API request, then verify that public links preserve github.com or provide an Open in browser fallback, including the enterprise-host scenario.

Written by the indexing model from the issue text.