[SOLVED] Shinylive won't allow downloading data tables as csv files

When I run this shinylive app on my local machine (Windows 11), it allows me to create a Gantt chart and table, which I can then download to a csv file. But when I host it on a GitHub page and click the download button, a download window opens, indicating there's no file. From the image, it appears that .htm is being tacked on to the csv file. I'm not very familiar with Java or HTML, so any suggestions how to change the R code in the app.R would be appreciated.

See for yourself. Shinylive Gantt on GitHub

I've tried a few things on my local machine by running the R script at the bottom (to create the other files shinylive needs in a folder called docs and run the app) every time I change the app.R file. This avoids commits to my remote repo every time I try something new.

library(tidyverse)
library(ggplot2)
library(DT)
library(shiny)
library(glue)
library(WriteXLS)

## source application files
#source("global.R", local = TRUE)


ui <- fluidPage(
 sidebarLayout(
  sidebarPanel(
   tags$h3("Project Gantt Chart"),
   tags$h4("Add or remove as many tasks as you like for a single project."),
   tags$hr(),
   textInput(inputId = "projectName", label = "Project Name:", placeholder = "e.g., My Project"),
   textInput(inputId = "inTaskName", label = "Task:", placeholder = "e.g., Extract and Link Data"),
   dateInput(inputId = "inStartDate", value = Sys.Date(), min = Sys.Date() - 365, label = "Start Date:"),
   dateInput(inputId = "inEndDate", value = Sys.Date() + 10, min = Sys.Date() - 364, label = "End Date:"),
   actionButton(inputId = "btn", label = "Add Task")
  ),
  mainPanel(
   tags$h3("Task Table View"),
   tags$hr(),
   DTOutput(outputId = "tableTasks"),
   downloadButton("downloadCSV", "Download Table as CSV file"),
   tags$h3("Gantt Chart"),
   tags$h4("Right-click the Gantt chart to copy or save as image."),
   tags$hr(),
   plotOutput(outputId = "plotTasks")
  )
 )
)


server <- function(input, output) {
 df <- reactiveValues(
  data = data.frame(
   Task = c("Task 1", "Task 2"),
   StartDate = as.Date(c("2024-03-10", "2024-04-30")),
   EndDate = as.Date(c("2024-04-30", "2024-06-15"))
  ) %>%
   # Add an ID column - used later to remove row with certain ID
   mutate(ID = row_number(), .before = Task) %>%
   # Add a column with a custom Remove button
   mutate(Remove = glue('<button id="custom_btn_{ID}" onclick="Shiny.onInputChange(\'button_id\', \'{ID}\')">Remove</button>'))
  
 )
 
 observeEvent(input$btn, {
  task_name <- input$inTaskName
  task_start_date <- input$inStartDate
  task_end_date <- input$inEndDate
  
  if (!is.null(task_name) && !is.null(task_start_date) && !is.null(task_end_date)) {
   # We also need a new row ID
   new_id <- nrow(df$data) + 1
   new_row <- data.frame(
    # Row ID
    ID = new_id,
    Task = task_name,
    StartDate = task_start_date,
    EndDate = task_end_date,
    # Remove button with a unique timestamp ID
    Remove = glue('<button id="custom_btn" onclick="Shiny.onInputChange(\'button_id\', \'{new_id}_', Sys.time(), '\')">Remove</button>'),
    stringsAsFactors = FALSE
   )
   df$data <- rbind(df$data, new_row)
   df$data <- df$data[order(df$data$ID), ]
  }
 })
 
 # REMOVE A TASK
 observeEvent(input$button_id, {
  # Extract the actual ID from the combined ID_timestamp
  actual_id <- unlist(strsplit(input$button_id, "_"))[1]
  
  # Remove a row from the data.frame
  df$data <- df$data[-c(as.integer(actual_id)), ]
  
  # Renumber the IDs
  df$data$ID <- seq_len(nrow(df$data))
  
  # Sort the dataframe by StartDate
  df$data <- df$data[order(df$data$StartDate), ]
  
  # Reset row names
  rownames(df$data) <- NULL
  
  # Update the Remove buttons to reflect new IDs with a unique timestamp
  df$data$Remove <- sapply(df$data$ID, function(i) {
   glue('<button id="custom_btn_{i}" onclick="Shiny.onInputChange(\'button_id\', \'{i}_', Sys.time(), '\')">Remove</button>')
  })
 })
 
 
 output$tableTasks <- renderDT({
  datatable(data = df$data, escape = FALSE, caption = input$projectName)
 })
 
 output$plotTasks <- renderPlot({
  ggplot(df$data, aes(x = StartDate, xend = EndDate, y = fct_rev(fct_inorder(Task)), yend = Task)) +
   geom_segment(linewidth = 10, color = "#0198f9") +
   labs(
    title = input$projectName,
    x = "Duration",
    y = "Task"
   ) +
   theme_bw() +
   theme(legend.position = "none") +
   theme(
    plot.title = element_text(size = 20),
    axis.text.x = element_text(size = 14),
    axis.text.y = element_text(size = 14)
   )
 })
 
 output$downloadCSV <- downloadHandler(
  filename = function() {
   paste("TaskData-", Sys.Date(), ".csv", sep="")
  },
  content = function(file) {
   write.csv(df$data, file, row.names=FALSE)
  },
  contentType = "text/csv"
 )
 
}

shinyApp(ui = ui, server = server)

Run the Shinylive app locally

# This file is saved in the directory for the local repo, which I called ShinyliveGantt
# The app.R is saved in Gantt
# Shinylive creates files in docs

# Load libraries
library(shinylive)
library(httpuv)

## Convert the shiny app into the assets for running the app in a browser

shinylive::export(
 appdir = "Gantt",
 destdir = "docs"
)

## Run the following in an R session to serve the app:
httpuv::runStaticServer("docs")

It seems like contentType = "text/csv" is being ignored. Most other questions I see on SO are related to loading files. I suspect there may be some way to change the downloadHandler command, but I haven't found it.