Bad shortcode syntax on a page breaks variable substitution

Bug description

Good shortcode: {{< shortcode >}}
Bad shortcode: {{< shortcode > }} notice the space after >.

If:

1. A project title (in _quarto.yml) contains a variable from _variables.yml
2. A page has a bad shortcode syntax (not necessarily a var shortcode)

then the project title in the header of that (2.) page will not be processed.

The same is true if using an environment variable in the _environment file.

Steps to reproduce

1. Create a quarto project.
2. Add the "bad" shortcode to a page.
3. Create variables file
4. Change project title to a var value
5. Render
6. Check the rendered title

On macos

quarto create project website . --no-prompt;
echo "{{< shortcode > }}" >> index.qmd;
echo "version: 1.2.3" >> _variables.yml;
sed -i '' -e 's/  title: "."/  title: "{{< var version >}}"/' _quarto.yml;  # macos sed
quarto render;
grep "navbar-title" _site/index.html

Alternatively, on linux

quarto create project website . --no-prompt;
echo "{{< shortcode > }}" >> index.qmd;
echo "version: 1.2.3" >> _variables.yml;
sed -i 's/  title: "."/  title: "{{< var version >}}"/' _quarto.yml;  # gnu sed
quarto render;
grep "navbar-title" _site/index.html

Expected behavior

    <span class="navbar-title">1.2.3</span>

Actual behavior

    <span class="navbar-title">{{&lt; var version &gt;}}</span>

Your environment

• OS: macOS Sonoma 14.1.1

Quarto check output

Quarto 1.4.530
[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.1.11: OK
      Dart Sass version 1.69.5: OK
      Deno version 1.37.2: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 1.4.530
      Path: /Applications/quarto/bin

[✓] Checking tools....................OK
      TinyTeX: v2022.11
      Chromium: (not installed)

[✓] Checking LaTeX....................OK
      Using: TinyTex
      Path: /Users/hassan/Library/TinyTeX/bin/universal-darwin
      Version: 2022

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

[✓] Checking Python 3 installation....OK
      Version: 3.11.4
      Path: /Users/hassan/.pyenv/versions/plotnine/bin/python3
      Jupyter: 5.5.0
      Kernels: gnuplot, python3

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

[✓] Checking R installation...........OK
      Version: 4.2.3
      Path: /Library/Frameworks/R.framework/Resources
      LibPaths:
        - /Library/Frameworks/R.framework/Versions/4.2/Resources/library
      knitr: 1.43
      rmarkdown: 2.21

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

Run the provided macOS or Linux reproduction using _quarto.yml, index.qmd, and _variables.yml, then compare the rendered navbar-title with the expected 1.2.3 value. Trace how the malformed shortcode in index.qmd is handled before variable substitution and rendering; done means the project title is substituted correctly despite the bad shortcode syntax, including when using _environment.