Incorrect "format" YAML value and maybe other fields only shows the first of many possible values

Bug description

This is originally at https://github.com/rstudio/rstudio/issues/11871

Error for the format field (and possibly others) in YAML only shows one possible value and states that it's the only possible value.

Steps to reproduce

1. Create a Quarto document with the following bad YAML content and save it.

---
title: "Untitled"
editor: sss
format: markdow
---

2. View in source or visual mode.
3. Hover over the error icon next to the editor field. (This example uses source mode, but it's the same in visual mode.)
   • The info message identifies both possible values, source and visual.

4. Hover over the error icon next to the format field. (This example uses visual mode, but it's the same in source mode.)
   • Only one item is identified as a possible value, asciidoc, even though there are dozens of possibilities.
   • The item shown is always the first one alphabetically, asciidoc, even though there are several possible legitimate values beginning with markdo, such as markdown, markdown_github, and others.

Expected behavior

Either

1. All possible values should be shown.
2. This would probably look awful for something with a whole bunch of possible values—as is the case with the format field—so the error should probably not mention the possible values. (They're available with autocompletion.)

Actual behavior

Error for the format field (and possibly others) in YAML only shows one possible value and states that it's the only possible value.

Your environment

RStudio Edition : Desktop
RStudio Version : 2022.11.0-daily+153 and 2023.09.0+463
OS Version      : MacOS 13 and MacOS 14
R Version       : 4.2.1 and 4.3.1

Quarto check output

[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.1.1: OK
      Dart Sass version 1.55.0: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 1.3.433
      Path: /Applications/RStudio-2023.09.0-463.app/Contents/Resources/app/quarto/bin

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

[✓] Checking Python 3 installation....OK
      Version: 3.11.4
      Path: /usr/local/opt/python@3.11/bin/python3.11
      Jupyter: (None)

      Jupyter is not available in this Python installation.
      Install with python3 -m pip install jupyter

[✓] Checking R installation...........OK
      Version: 4.3.1
      Path: /Library/Frameworks/R.framework/Resources
      LibPaths:
        - /Users/ronblum/Library/R/x86_64/4.3/library
        - /Library/Frameworks/R.framework/Versions/4.3-x86_64/Resources/library
      knitr: 1.44
      rmarkdown: 2.25

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