There are two symbols for separating transforms in a pipeline - \n and | so you can use | instead of \n if you prefer.

So for your query from the linked gist, the following should work:

    from system.numbers | select number

Otherwise, if you want to be really strict:

    prql target:sql.clickhouse

    from `system.numbers` | select {number}

You can see here for more details: https://prql-lang.org/book/reference/syntax/keywords.html