Render should error if not called within output

Currently this application will run but not produce any results. Seems like we should have an error here.

from shiny import Inputs, Outputs, Session, App, ui, render
import pandas as pd
from pathlib import Path

infile = Path(__file__).parent / "penguins.csv"
penguins = pd.read_csv(infile)

app_ui = ui.page_fluid(ui.output_data_frame("penguins_df"))


def server(input: Inputs, output: Outputs, session: Session):
    @render.data_frame
    @output
    def my_df():
        return penguins


app = App(app_ui, server)

Reproduce the behavior with the supplied Python example, starting at the server function and the @render.data_frame and @output decorators. Trace how the output is registered and determine where this usage can be detected; done means the application raises a clear error instead of running without results.