`quarto-render --fail-if-warnings` not working as expected

I want things like misspelled filenames to trigger an error, especially in a CI job (which is awesome BTW https://github.com/quarto-dev/quarto-cli/discussions/439).

However, I don't get the non-zero exit code I would expect:

$ quarto render --fail-if-warnings
[ 1/14] file1.md
[ 2/14] file2.md
...
WARNING: Unable to resolve link target: intentional-typo.md
...
[13/14] file13.md
[14/14] file14.md

Output created: docs/index.html

$ echo $?
0

$ quarto --version
0.9.171

Start by reproducing the reported command with quarto render --fail-if-warnings and the unresolved intentional-typo.md link, using Quarto 0.9.171 or a current checkout. Trace how the warning affects the render command's exit status; done means the command returns non-zero when this warning occurs, suitable for CI.