@Persist state returns RpcStub objects when returned via RPC

## Problem

When an Actor method returns `@Persist` decorated state via RPC, the caller receives `RpcStub` objects instead of serialized data.

## Reproduction

https://github.com/dmmulroy/actor-bug

```bash
git clone https://github.com/dmmulroy/actor-bug
cd actor-bug
npm install
npm run dev
curl http://localhost:8787
```

### DataActor.ts

```ts
import { Actor, Persist } from "@cloudflare/actors";

type Item = { id: string; value: number };

export class DataActor extends Actor {
@Persist state: { items: Item[] } = { items: [] };

async getItems(): Promise {
return this.state.items; // Returns RpcStub objects to RPC callers
}
}
```

### CoordinatorActor.ts (RPC caller)

```ts
const dataActor = DataActor.get("data-1");
const items = await dataActor.getItems();

console.log(items); // [ RpcStub {}, RpcStub {} ]
console.log(typeof items[0]); // "function"
console.log(String(items[0])); // "[object JsRpcStub]"
```

## Expected

`getItems()` returns `[{ id: "item-1", value: 100 }, ...]`

## Actual

`getItems()` returns `[RpcStub {}, RpcStub {}]` which serialize to `[null, null]`

## Workarounds

### 1. Query storage directly (recommended)

```ts
async getItems(): Promise {
const result = this.ctx.storage.sql.exec(
"SELECT value FROM _actor_persist WHERE property = 'state'"
);
const row = [...result][0];
if (row) {
return JSON.parse(row.value as string).items ?? [];
}
return [];
}
```

### 2. JSON roundtrip

```ts
async getItems(): Promise {
return JSON.parse(JSON.stringify(this.state.items));
}
```

## Environment

- `@cloudflare/actors`: 0.0.1-beta.6
- `wrangler`: 4.53.0