reactive.event does not work in Quarto dashboard

Bug description

@reactive.event used in a Quarto dashboard does not seem to work. The following Quarto document fails when rendered:

---
title: "Test dashboard"
format: dashboard
server: shiny
---

# {.sidebar }

```{python}
from shiny import reactive
from shiny.express import input, ui, render

ui.input_text_area("text", "Text", value="hello")
ui.input_action_button("loadtext", "Load text")
```
```{python}
@render.text
@reactive.event(input.loadtext)
def set_text():    
    return input.text()
```

Steps to reproduce

• Save file in bug description above in quarto.qmd
• Do quarto render quarto.qmd

gives the error message:

---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
Cell In[2], line 2
      1 @render.text
----> 2 @reactive.event(input.loadtext)
      3 def set_text():    
      4     return input.text()

File ~/.local/lib/python3.12/site-packages/shiny/express/__init__.py:76, in _ExpressOnlyPlaceholder.__getattr__(self, name)
     75 def __getattr__(self, name: str) -> None:
---> 76     raise RuntimeError(
     77         f"shiny.express.{self.name} can only be used inside of a Shiny Express app."
     78     )

RuntimeError: shiny.express.input can only be used inside of a Shiny Express app.

Actual behavior

gives the error message:

---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
Cell In[2], line 2
      1 @render.text
----> 2 @reactive.event(input.loadtext)
      3 def set_text():    
      4     return input.text()

File ~/.local/lib/python3.12/site-packages/shiny/express/__init__.py:76, in _ExpressOnlyPlaceholder.__getattr__(self, name)
     75 def __getattr__(self, name: str) -> None:
---> 76     raise RuntimeError(
     77         f"shiny.express.{self.name} can only be used inside of a Shiny Express app."
     78     )

RuntimeError: shiny.express.input can only be used inside of a Shiny Express app.

Expected behavior

A Quarto dashboard GUI without errors.

Your environment

• IDE: VScode 1.89.1
• Quarto: 1.6.42
• Shiny: 1.3.0
• Python: 3.12.3

Quarto check output

Quarto 1.6.42
[✓] Checking environment information...
      Quarto cache location: /home/pjds/.cache/quarto
[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.4.0: OK
      Dart Sass version 1.70.0: OK
      Deno version 1.46.3: OK
      Typst version 0.11.0: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 1.6.42
      Path: /opt/quarto/bin

[✓] Checking tools....................OK
      TinyTeX: v2025.02
      Chromium: (not installed)

[✓] Checking LaTeX....................OK
      Using: TinyTex
      Path: /home/pjds/.TinyTeX/bin/x86_64-linux
      Version: 2024

[✓] Checking basic markdown render....OK

[✓] Checking Python 3 installation....OK
      Version: 3.12.3
      Path: /usr/bin/python3
      Jupyter: 5.7.2
      Kernels: minerva_4.0.0-beta393, minerva_4.0.0-beta392, minerva, python3

[✓] Checking Jupyter engine render....OK

[✓] Checking R installation...........(None)

      Unable to locate an installed version of R.
      Install R from https://cloud.r-project.org/

Start by saving the supplied example as quarto.qmd and running quarto render quarto.qmd with the listed Quarto, Shiny, and Python versions. Trace how the Python cells, reactive.event(input.loadtext), and the Quarto dashboard server interact. Done means the document renders without the shiny.express.input RuntimeError and the dashboard behaves as expected.