dotnet watch cannot Hot Reload scoped CSS from a hosted Blazor WebAssembly client project

### Describe the bug

When an ASP.NET Core server hosts a referenced Blazor WebAssembly client, saving a `.razor.css` file in the client produces this warning:

```text
[ScopedCssHotReloadRepro.Server (net10.0)] Scoped CSS bundle file 'ScopedCssHotReloadRepro.Client.bundle.scp.css' not found.
```

The scoped-CSS change isn't applied to the running application. A full rebuild/restart generates and serves the updated CSS correctly.

### Steps to reproduce

Minimal reproduction project:
[ScopedCssHotReloadMissingBundle.zip](https://github.com/user-attachments/files/31890788/ScopedCssHotReloadMissingBundle.zip)

1. Use the attached minimal reproduction, which contains:
- `Server`: `Microsoft.NET.Sdk.Web`, targeting `net10.0`.
- `Client`: `Microsoft.NET.Sdk.BlazorWebAssembly`, targeting `net10.0`.
- A project reference from `Server` to `Client`.
- A Razor component and matching `.razor.css` file in `Client`.
2. Run:

```powershell
dotnet watch --project Server/ScopedCssHotReloadRepro.Server.csproj
```

3. Open the application in a browser.
4. Change any css in `Client/Pages/ScopedCssDemo.razor.css` and save.

### Expected behavior

The client scoped-CSS bundle is regenerated and the running browser displays the new css without restarting the application.

### Actual behavior

`dotnet watch` logs the missing-bundle warning shown above, the generated scoped-CSS bundle remains stale, and the browser continues to display the old style until the application is rebuilt and restarted.

### Is this a regression?

Yes this setup was working perfectly find in dotnet 9 versions and earlier, verified on the repro project on sdk version 9.0.308.

### Are there any workarounds?

_No response_

### dotnet --info output

```console
.NET SDK:
Version: 10.0.400
Commit: 14fbf8d527
Workload version: 10.0.400
MSBuild version: 18.9.6+14fbf8d52

Runtime Environment:
OS Name: Windows
OS Version: 10.0.26200
OS Platform: Windows
RID: win-x64
Base Path: C:\Program Files\dotnet\sdk\10.0.400\

.NET workloads installed:
[maui-android]
Installation Source: SDK 10.0.400
Manifest Version: 10.0.20/10.0.100
Manifest Path: C:\Program Files\dotnet\sdk-manifests\10.0.100\microsoft.net.sdk.maui\10.0.20\WorkloadManifest.json
Install Type: Msi

[maui-tizen]
Installation Source: SDK 10.0.400
Manifest Version: 10.0.20/10.0.100
Manifest Path: C:\Program Files\dotnet\sdk-manifests\10.0.100\microsoft.net.sdk.maui\10.0.20\WorkloadManifest.json
Install Type: Msi

Configured to use workload sets when installing new manifests.

Host:
Version: 10.0.11
Architecture: x64
Commit: e2f47b0110

.NET SDKs installed:
8.0.417 [C:\Program Files\dotnet\sdk]
9.0.308 [C:\Program Files\dotnet\sdk]
10.0.200 [C:\Program Files\dotnet\sdk]
10.0.303 [C:\Program Files\dotnet\sdk]
10.0.400 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 8.0.23 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 9.0.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 10.0.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 10.0.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 8.0.23 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 9.0.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 10.0.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 10.0.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 8.0.23 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 9.0.11 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 10.0.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 10.0.11 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
x86 [C:\Program Files (x86)\dotnet]
registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
Not set

global.json file:
Not found

Learn more:
https://aka.ms/dotnet/info

Download .NET:
https://aka.ms/dotnet/download
```

### IDE version

Rider 2026.2.1

### Other details

_No response_

Extract the attached ScopedCssHotReloadMissingBundle.zip and start by running dotnet watch --project Server/ScopedCssHotReloadRepro.Server.csproj. Change Client/Pages/ScopedCssDemo.razor.css and inspect the watch output and generated bundle behavior. Done means the client scoped-CSS bundle updates and the running browser displays the change without a restart.

Written by the indexing model from the issue text.