Use local dotnet-ef tooling and strict EF migration checks

README.md

@@ -42,6 +42,7 @@ Backend state persistence:
 
 - .NET SDK 10.0+
 - PowerShell 7+
+- Run `dotnet tool restore` once to enable the repo-local `dotnet-ef` command.
 
 ## Local Development
 
@@ -63,6 +64,12 @@ VS Code F5 debug profiles are available in `.vscode/launch.json`:
 
 To use a custom SQLite database path, set `ConnectionStrings__RpgRoller`.
 
+For migration authoring, use the local tool command form:
+
+```powershell
+dotnet dotnet-ef migrations add <MigrationName> --project RpgRoller/RpgRoller.csproj --startup-project RpgRoller/RpgRoller.csproj
+```
+
 ## Frontend Runtime
 
 - Runtime frontend is Blazor Server with interactive components.