src/
├── actions/           # Domain Layer: Business Logic (Actions)
│   ├── Action.ts      # Base Action class
│   └── [Domain]/      # Domain-specific actions
├── controllers/       # Responder Layer: HTTP Handlers
│   └── api/v1/        # API Controllers (Thin)
├── models/            # Domain: Atlas Models
├── repositories/      # Domain: Data Access
├── types/             # Contracts
│   ├── requests/      # Typed request bodies
│   └── responses/     # Typed response bodies
└── routes/            # Route Definitions

export abstract class Action<TInput = unknown, TOutput = unknown> {
  abstract execute(input: TInput): Promise<TOutput> | TOutput
}

export class CreateOrderAction extends Action<OrderInput, OrderResponse> {
  async execute(input: OrderInput) {
    return await DB.transaction(async (trx) => {
      // 1. Validate...
      // 2. Persist...
      // 3. Trigger events...
    })
  }
}