Inaccessible `copilotd` release link in WSL Hosts setup

The WSL Hosts setup screen instructs users to download `copilotd` from: https://github.com/github/copilot-host/releases but that URL returns a 404.

### Steps to reproduce

1. Open GitHub Copilot App on Windows.
2. Go to the WSL Hosts setup/registration screen.
3. Click the `copilotd releases` link shown in the instructions.
4. Observe that the GitHub releases page returns 404.

### Actual behavior

The provided link is inaccessible:

https://github.com/github/copilot-host/releases

This blocks WSL host setup because the UI says `copilotd` must be installed inside the distro and available on PATH.

### Expected behavior

The app should link to a publicly accessible download page for the required `copilotd` binary, or provide another supported installation path.

### Additional context

The screen says:

> `copilotd` must be installed inside the distro and available on your login-shell PATH. Download a matching build from the `copilotd releases` page (this app is pinned to `copilotd v0.5.4`)...

Example command shown:

```bash
chmod +x ~/.local/bin/copilotd

Start at the WSL Hosts setup/registration screen and trace the displayed `copilotd releases` link and installation instructions. Verify the current URL and the `copilotd v0.5.4` requirement; done when the screen points to a publicly accessible download or supported installation path and the link no longer returns 404.

索引モデルが issue の本文から書いたものです。