Fix TypeScript compilation error: remove duplicate 'default' property in august-yale mock (#172)

Fixes a TypeScript compilation error in `src/platform.test.ts` where the
august-yale module mock had duplicate `default` properties in the same
object literal:

```typescript
// Before (compilation error)
return {
  default: class August { ... },  // First default property
  default: MockConstructor,       // Second default property - DUPLICATE!
}

// After (fixed)
return {
  default: MockConstructor,
}
```

The error was:
```
src/platform.test.ts:35:5 - error TS1117: An object literal cannot have multiple properties with the same name.
```

The fix removes the redundant class definition and keeps only the
`MockConstructor` as the default export, which already provides all the
necessary static methods (`authorize`, `validate`, `details`) for
testing. All existing tests continue to pass.

Fixes #171.

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---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: Donavan Becker <[email protected]>
Co-authored-by: donavanbecker <[email protected]>

Author: Copilot

src/platform.test.ts

@@ -23,15 +23,6 @@ vi.mock('august-yale', () => {
   MockConstructor.validate = vi.fn()
 
   return {
-    default: class August {
-      public credentials: any
-      constructor(credentials: any) {
-        this.credentials = credentials
-      }
-      static async authorize() {}
-      static async validate() { return true }
-      static async details() { return [] }
-    },
     default: MockConstructor,
   }
 })