Programmatic Scaffold-Migration Broken After Updating from 8.0.15 to 9.0.4

### Bug description

project: [ProgrammaticalScaffold.zip](https://github.com/user-attachments/files/19980137/ProgrammaticalScaffold.zip)

1- run Update-Database to apply the first migration.
2- try to scaffold a new migration (one column added) by clicking on the scaffold button in the Home page.
Expected result:
A new migration script file that only contains AddColumn (the newly added column).
Actual result:
A new migration file containing a complete model snapshot instead of just the incremental change.

### Your code

```csharp
public async Task ScaffoldMigration()
{
try
{
var assemblyTypes = AppDomain.CurrentDomain.GetAssemblies().FirstOrDefault(a => a.FullName.Contains($"WebApplication"))?.GetTypes();

var dbContextType = assemblyTypes?.FirstOrDefault(a => a.FullName == $"WebApplication.ApplicationDbContext");

if (dbContextType is null)
{
return;
}

var dbContext = HttpContext.RequestServices.GetService(dbContextType) as DbContext;
var relationalDatabaseCreator = dbContext.GetService() as IRelationalDatabaseCreator;

if (!await relationalDatabaseCreator.ExistsAsync() || dbContext.Database.HasPendingModelChanges())
{
var migrations = dbContext.Database.GetMigrations();
var services = new ServiceCollection().AddEntityFrameworkDesignTimeServices().AddDbContextDesignTimeServices(dbContext);

var designTimeServices = new SqlServerDesignTimeServices();
designTimeServices.ConfigureDesignTimeServices(services);

var scaffolder = services.BuildServiceProvider().GetRequiredService();

var migrationPath = Path.Combine(_hosting.ContentRootPath, "Migrations");
Directory.CreateDirectory(migrationPath);

var nextMigrationNumber = 3;

var migration = scaffolder.ScaffoldMigration($"Migration-{nextMigrationNumber:D3}", $"WebApplication", $"Migrations");

await Task.WhenAll(
System.IO.File.WriteAllTextAsync(Path.Combine(migrationPath, migration.MigrationId + migration.FileExtension),
migration.MigrationCode),
System.IO.File.WriteAllTextAsync(Path.Combine(migrationPath, migration.MigrationId + ".Designer" + migration.FileExtension),
migration.MetadataCode),
System.IO.File.WriteAllTextAsync(Path.Combine(migrationPath, migration.SnapshotName + migration.FileExtension),
migration.SnapshotCode)
);
}
}
catch { }
}
```

### Stack traces

```text

```

### Verbose output

```text

```

### EF Core version

9.0.4

### Database provider

SqlServer

### Target framework

.NET 9

### Operating system

Windows 11

### IDE

_No response_