.MapRazorComponents<App>().AddAdditionalAssemblies() not working when <Router> has @rendermode = InteractiveServer

Is there an existing issue for this?

[X] I have searched the existing issues

Describe the bug

This might be related to #46980. Pages defined in a RCL that has been added as an additional assembly to .MapRazorComponents<>(), using .AddAdditionalAssemblies() are not reachable if the router has @rendermode="InteractiveServer".

Expected Behavior

Pages defined in the RCL should be reachable regardless of @rendermode

Steps To Reproduce

Create a new "Blazor Web App" from template using Interactive render mode = Server and Interactivity location = Per page/component.
Add a RCL with a .razor file that has @page "/custompath"
Add this RCL as an additional assembly in Razor component mapping.
Start the Web App and see that /custompath is reachable
Add @rendermode=InteractiveServer to <Routes /> in App.razor
Start the Web App and observe that /custompath is not reachable (It enters the <NotFound> section in the <Router> if it exists)

Exceptions (if any)

N/A

.NET Version

8.0.303

Anything else?

ASP.NET Core version: 8.0.7 IDE: Visual Studio Professional 2022 (64-bit) 17.10.4 dotnet --info:

.NET SDK:
 Version:           8.0.303
 Commit:            29ab8e3268
 Workload version:  8.0.300-manifests.34944930
 MSBuild version:   17.10.4+10fbfbf2e

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.22631
 OS Platform: Windows
 RID:         win-x64
 Base Path:   C:\Program Files\dotnet\sdk\8.0.303\

.NET workloads installed:
 [wasm-tools-net6]
   Installation Source: VS 17.10.35027.167
   Manifest Version:    8.0.7/8.0.100
   Manifest Path:       C:\Program Files\dotnet\sdk-manifests\8.0.100\microsoft.net.workload.mono.toolchain.net6\8.0.7\WorkloadManifest.json
   Install Type:        FileBased

 [wasm-tools]
   Installation Source: VS 17.10.35027.167
   Manifest Version:    8.0.7/8.0.100
   Manifest Path:       C:\Program Files\dotnet\sdk-manifests\8.0.100\microsoft.net.workload.mono.toolchain.current\8.0.7\WorkloadManifest.json
   Install Type:        FileBased

 [android]
   Installation Source: VS 17.10.35027.167
   Manifest Version:    34.0.95/8.0.100
   Manifest Path:       C:\Program Files\dotnet\sdk-manifests\8.0.100\microsoft.net.sdk.android\34.0.95\WorkloadManifest.json
   Install Type:        FileBased

 [maui-windows]
   Installation Source: VS 17.10.35027.167
   Manifest Version:    8.0.61/8.0.100
   Manifest Path:       C:\Program Files\dotnet\sdk-manifests\8.0.100\microsoft.net.sdk.maui\8.0.61\WorkloadManifest.json
   Install Type:        FileBased

 [aspire]
   Installation Source: VS 17.10.35027.167
   Manifest Version:    8.0.0/8.0.100
   Manifest Path:       C:\Program Files\dotnet\sdk-manifests\8.0.100\microsoft.net.sdk.aspire\8.0.0\WorkloadManifest.json
   Install Type:        FileBased

 [maccatalyst]
   Installation Source: VS 17.10.35027.167
   Manifest Version:    17.2.8053/8.0.100
   Manifest Path:       C:\Program Files\dotnet\sdk-manifests\8.0.100\microsoft.net.sdk.maccatalyst\17.2.8053\WorkloadManifest.json
   Install Type:        FileBased

 [ios]
   Installation Source: VS 17.10.35027.167
   Manifest Version:    17.2.8053/8.0.100
   Manifest Path:       C:\Program Files\dotnet\sdk-manifests\8.0.100\microsoft.net.sdk.ios\17.2.8053\WorkloadManifest.json
   Install Type:        FileBased

Host:
  Version:      8.0.7
  Architecture: x64
  Commit:       2aade6beb0

.NET SDKs installed:
  8.0.303 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 3.1.32 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 6.0.32 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 8.0.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 3.1.32 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.18 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.32 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 8.0.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.1.32 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 6.0.18 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 6.0.32 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 8.0.7 [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

dotnet / aspnetcore

.MapRazorComponents<App>().AddAdditionalAssemblies() not working when <Router> has @rendermode = InteractiveServer #57265