`pdf-standard` leads to stacktrace

[mcanouil]

I have:

• searched the issue tracker for similar issues
• installed the latest version of Quarto CLI
• formatted my issue following the Bug Reports guide

Bug description

Setting pdf-standard leads to stacktrace when it is not validated.

echo "{{< placeholder >}}" > example.qmd
quarto render example.qmd --to typst -M "pdf-standard: ua-1"

pandoc 
  to: typst
  output-file: example.typ
  standalone: true
  shift-heading-level-by: -1
  default-image-extension: svg
  wrap: none
  citeproc: false
  variables: {}
  
metadata
  pdf-standard: ua-1
  
[typst]: Compiling example.typ to example.pdf...error: PDF/UA-1 error: missing alt text
    ┌─ example.typ:338:5
    │
338 │ #box(image("example_files/mediabag/svg-xml-base64,PHN2Z.svg"))
    │      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    │
    = hint: make sure your images and equations have alt text

error: PDF/UA-1 error: missing document title
 = hint: set the title with `set document(title: [...])`

ERROR: error: PDF/UA-1 error: missing alt text
    ┌─ example.typ:338:5
    │
338 │ #box(image("example_files/mediabag/svg-xml-base64,PHN2Z.svg"))
    │      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    │
    = hint: make sure your images and equations have alt text

error: PDF/UA-1 error: missing document title
 = hint: set the title with `set document(title: [...])`


ERROR: Typst compilation failed

Stack trace:
    at Object.complete (file:///Users/mcanouil/Projects/quarto-dev/quarto-cli/src/command/render/output-typst.ts:168:13)
    at eventLoopTick (ext:core/01_core.js:179:7)
    at async file:///Users/mcanouil/Projects/quarto-dev/quarto-cli/src/command/render/render.ts:302:23
    at async withTimingAsync (file:///Users/mcanouil/Projects/quarto-dev/quarto-cli/src/core/timing.ts:47:20)
    at async Object.complete (file:///Users/mcanouil/Projects/quarto-dev/quarto-cli/src/command/render/render.ts:278:7)
    at async Object.onPostProcess (file:///Users/mcanouil/Projects/quarto-dev/quarto-cli/src/command/render/render-files.ts:735:28)
    at async renderFileInternal (file:///Users/mcanouil/Projects/quarto-dev/quarto-cli/src/command/render/render-files.ts:704:3)
    at async renderFiles (file:///Users/mcanouil/Projects/quarto-dev/quarto-cli/src/command/render/render-files.ts:330:9)
    at async render (file:///Users/mcanouil/Projects/quarto-dev/quarto-cli/src/command/render/render-shared.ts:109:18)
    at async Command.actionHandler (file:///Users/mcanouil/Projects/quarto-dev/quarto-cli/src/command/render/cmd.ts:251:26)
    at async Command.execute (https://deno.land/x/cliffy@v1.0.0-rc.3/command/command.ts:1948:7)
    at async Command.parseCommand (https://deno.land/x/cliffy@v1.0.0-rc.3/command/command.ts:1780:14)
    at async quarto (file:///Users/mcanouil/Projects/quarto-dev/quarto-cli/src/quarto.ts:198:5)
    at async file:///Users/mcanouil/Projects/quarto-dev/quarto-cli/src/quarto.ts:230:5
    at async file:///Users/mcanouil/Projects/quarto-dev/quarto-cli/src/core/main.ts:45:14
    at async mainRunner (file:///Users/mcanouil/Projects/quarto-dev/quarto-cli/src/core/main.ts:47:5)
    at async file:///Users/mcanouil/Projects/quarto-dev/quarto-cli/src/quarto.ts:220:3

Quarto check output

Quarto 99.9.9
[✓] Checking environment information...
      Quarto cache location: /Users/mcanouil/Library/Caches/quarto
[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.8.3: OK
      Dart Sass version 1.87.0: OK
      Deno version 2.4.5: OK
      Typst version 0.14.2: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 99.9.9
      commit: 4e7e8c831c183372d4056c7db52b5ffd2bf450be
      Path: /Users/mcanouil/Projects/quarto-dev/quarto-cli/package/dist/bin

[✓] Checking tools....................OK
      TinyTeX: v2026.01
      Chromium: (not installed)
      VeraPDF: (not installed)

[✓] Checking LaTeX....................OK
      Using: TinyTex
      Path: /Users/mcanouil/Library/TinyTeX/bin/universal-darwin
      Version: 2025

[✓] Checking Chrome Headless....................OK
      Using: Chrome found on system
      Path: /Applications/Brave Browser.app/Contents/MacOS/Brave Browser
      Source: QUARTO_CHROMIUM

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

(/) Checking R installation...........ℹ R version 4.5.2 (2025-10-31)
! Config '~/.Rprofile' was loaded!
[✓] Checking R installation...........OK
      Version: 4.5.2
      Path: /Library/Frameworks/R.framework/Resources
      LibPaths:
        - /Library/Frameworks/R.framework/Versions/4.5-arm64/Resources/library
      knitr: 1.50
      rmarkdown: 2.30

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

[✓] Checking Python 3 installation....OK
      Version: 3.14.2
      Path: /opt/homebrew/opt/python@3.14/bin/python3.14
      Jupyter: (None)

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

[✓] Checking Julia installation...