Quarto default style (arrow-light) for code does not highlight dsBuiltIn and dsExtension, where arrow-dark does

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

The quarto default code style (arrow-light) does not highlight BuiltIn or Extension, instead just presenting those code elements in all languages as default text. This is in contrast to most other themes, including the arrow-dark style.

I would expect (based on syntax highlighting documentation) they would minimally be highlighted using the same colours as Function/Variable/Other styles.

Steps to reproduce

Sample quarto doc with different languages, using default highlighting. In typst none/auto/true/false are all builtins. In python abs/dict are builtins, [:upper:] is an Extension, in terraform the functions are highlighted as builtins. In light mode these are all presented as normal text, in dark they get highlighting

---
highlight-style: arrow
theme:
  light: flatly
  dark: darkly
format:
  html:
    embed-resources: true
---

```typst
#let config = (
  debug: none,
  width: auto,
  visible: true,
)

#let show-box(width: auto, border: none, fill: false) = {
  let has-border = border != none
  box(width: width, stroke: if has-border { border } else { none })
}
```


```python
import re
from statistics import mean

x = abs(-5)

y = dict(
    z = 5,
    b = 1
)

z = mean((1,2,3))

s = re.compile(r"\w{2}\d+[[:upper:]]*")
```

```terraform
locals {
  name    = trimprefix(upper("  hello-world  "), " ")
  offset  = abs(-42)
  items   = sort(["banana", "apple", "cherry"])
  joined  = join(", ", local.items)
  hash    = substr(sha256("my-id"), 0, 8)
}
```

test.html

Actual behavior

See attached HTML files

Expected behavior

I would expect the arrow-light.theme in src\resources\pandoc\highlight-styles to define text-color for BuiltIn and Extension, rather than leaving it null.

The arrow-dark.theme does colour BuiltIn and Extension - making them the same colours as Char and Variable respectively. This could be replicated in the light theme for consistency, or alternatively I would expect using the Function colours for both would improve the situation without being over coloured.

Your environment

• IDE: Positron 2026.03.0
• OS: Windows 11

Quarto check output

> quarto check
Quarto 1.8.27
[>] Checking environment information...
      Quarto cache location: C:\Users\Michael.Walshe\AppData\Local\quarto
[>] Checking versions of quarto binary dependencies...
      Pandoc version 3.6.3: OK
      Dart Sass version 1.87.0: OK
      Deno version 2.3.1: OK
      Typst version 0.13.0: OK
[>] Checking versions of quarto dependencies......OK
[>] Checking Quarto installation......OK
      Version: 1.8.27
      Path: C:\Program Files\Quarto\bin
      CodePage: 1252

[>] Checking tools....................OK
      TinyTeX: (external install)
      Chromium: (not installed)

[>] Checking LaTeX....................OK
      Using: TinyTex
      Path: C:\Users\Michael.Walshe\AppData\Roaming\TinyTeX\bin\windows\
      Version: 2024

[>] Checking Chrome Headless....................OK
      Using: Chrome found on system
      Path: C:\Program Files\Google\Chrome\Application\chrome.exe
      Source: Windows Registry

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

[>] Checking Python 3 installation....OK
      Version: 3.14.0
      Path: C:/Users/Michael.Walshe/AppData/Roaming/uv/python/cpython-3.14.0rc2-windows-x86_64-none/python.exe   
      Jupyter: (None)

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

[>] Checking R installation...........OK
      Version: 4.5.2
      Path: C:/PROGRA~1/R/R-45~1.2
      LibPaths:
        - C:/Users/Michael.Walshe/AppData/Local/R/win-library/4.5
        - C:/Program Files/R/R-4.5.2/library
      knitr: 1.51
      rmarkdown: 2.30

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

Open src/resources/pandoc/highlight-styles/arrow-light.theme and compare its BuiltIn and Extension entries with arrow-dark.theme. Verify the sample Quarto document in the issue, then confirm that the light style gives those elements a defined, consistent text color across the shown languages.