bug: squash::compile_qmd_course delete files that shouldn't be deleted

[ColinFay]

Description

Given the following _quarto.yml :

project:
  pre-render:
    - touch coucou.csv

coucou.csv is created by the quarto rendering, but suppressed on exit

for (i in 1:5){
  write(file = sprintf("test%s.qmd", i),
        sprintf("---
title: 'test%s'
---

## Quarto is cool", i)
  )
}

list.files(pattern = "\\.qmd$", full.names = TRUE, recursive = TRUE) |>
  squash::compile_qmd_course(
    output_dir = "mycoursehere",
    output_html = "complete_course.html"
  )