some messages are not objects but instead scalar values

Here is the latest export for `ExecuteMsg` (in Typescript)

```js
export type ExecuteMsg = {
mint: {
[k: string]: unknown;
};
} | {
set_whitelist: {
whitelist: string;
[k: string]: unknown;
};
} | {
update_start_time: Timestamp;
} | {
update_per_address_limit: {
per_address_limit: number;
[k: string]: unknown;
};
} | {
mint_to: {
recipient: string;
[k: string]: unknown;
};
} | {
mint_for: {
recipient: string;
token_id: number;
[k: string]: unknown;
};
} | {
withdraw: {
[k: string]: unknown;
};
};
```

I noticed that `update_start_time` is the only one that doesn't take an object. Every other message uses either an empty object or an object with props.

```
update_start_time: Timestamp
```

Is there a convention? Or should we account for this in the cosmwasm-typescript-gen

Start by tracing how cosmwasm-typescript-gen handles ExecuteMsg variants, comparing the scalar update_start_time value with the object-shaped messages shown in the report. Done means the generator either represents scalar message values correctly and consistently, or clearly documents the convention it follows.

索引モデルが issue の本文から書いたものです。