shiny-mediator

# Shiny Mediator Skill

You are an expert in Shiny Mediator, a mediator pattern library for .NET applications.

## When to Use This Skill

Invoke this skill when the user wants to:
- Create request handlers, command handlers, event handlers, or stream handlers
- Generate contracts (IRequest, ICommand, IEvent, IStreamRequest)
- Add middleware (caching, resilience, validation, offline)
- Scaffold ASP.NET, MAUI, or Blazor projects with Shiny Mediator
- Configure Shiny Mediator in their application
- Migrate from MediatR to Shiny Mediator

## Library Overview

**Documentation**: https://shinylib.net/mediator

Shiny Mediator is AOT & trimming friendly, using source generators for automatic DI registration.

### Core Patterns

| Pattern | Contract | Handler | Usage |
|---------|----------|---------|-------|
| Request | `IRequest<TResult>` | `IRequestHandler<TRequest, TResult>` | Queries returning data |
| Command | `ICommand` | `ICommandHandler<TCommand>` | Void state changes |
| Event | `IEvent` | `IEventHandler<TEvent>` | Pub/sub notifications |
| Stream | `IStreamRequest<TResult>` | `IStreamRequestHandler<TRequest, TResult>` | IAsyncEnumerable |

### Handler Registration

Always use registration attributes:
```csharp
[MediatorSingleton]  // Stateless handlers
[MediatorScoped]     // Handlers needing per-request services (DbContext)
```

**Critical: Partial Class Requirement**

When using **any middleware attribute** (`[Cache]`, `[OfflineAvailable]`, `[Resilient]`, `[MainThread]`, `[TimerRefresh]`), the handler class **must be declared as `partial`**:
```csharp
[MediatorSingleton]
public partial class MyHandler : IRequestHandler<MyRequest, MyResult>  // partial required!
{
    [Cache(AbsoluteExpirationSeconds = 60)]
    public Task<MyResult> Handle(...) { }
}
```
This enables the source generator to create the `IHandlerAttributeMarker` implementation. Without `partial`, you'll get error `SHINY001`.

### Basic Setup

**ASP.NET:**
```csharp
builder.Services.AddShinyMediat