Unnecessary local copies of Typst extensions [prerelease]

[CoryMcCartan]

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

Basic Typst documents that don't need any extensions still download the basic extensions to .quarto/, which creates 1.5MB of unecessary files.

Steps to reproduce

Create an empty directory and save the following as test.qmd

---
title: A test
format: 
    typst:
        keep-typ: true
---

Run quarto render test.qmd

Actual behavior

Opening test.typ confirms no use of any extensions.
But a .quarto/ directory is created with 6 bundled extensions weighing 1.5 MB (vs 65B for the qmd, 10kB for the typ, and 8 kB for the PDF)

Expected behavior

.quarto/typst/packages/ should only be created or non-empty if the extensions are needed to render the document. 1.5 MB overhead on every single document seems quite excessive.

Your environment

• OS: MacOS 15.7.4

Quarto check output

Quarto 1.9.23
[✓] Checking environment information...
      Quarto cache location: /Users/cmccartan/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: 1.9.23
      Path: /Applications/quarto/bin

[✓] Checking tools....................OK
      TinyTeX: (external install)
      Chromium: (not installed)
      Chrome Headless Shell: (not installed)
      VeraPDF: (not installed)

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

[✓] Checking Chrome Headless....................OK
      Using: Chrome found on system
      Path: /Applications/Google Chrome.app/Contents/MacOS/Google Chrome
      Source: MacOS known location

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

[✓] Checking R installation...........OK
      Version: 4.5.0
      Path: /Library/Frameworks/R.framework/Resources
      LibPaths:
        - /Library/Frameworks/R.framework/Versions/4.5-arm64/Resources/library
      knitr: 1.50
      rmarkdown: 2.29

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

[✓] Checking Python 3 installation....OK
      Version: 3.9.6
      Path: /Library/Developer/CommandLineTools/usr/bin/python3
      Jupyter: (None)

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

[✓] Checking Julia installation...