Code cell numbering in embeds is invisible in dark themes

该问题位于Bootstrap主题的SCSS文件中。查看 src/resources/formats/html/bootstrap/_bootstrap-rules.scss 第949-953行，并与深色主题文件（如 darkly.scss 第184行）进行比较。修复方法是确保在深色主题中 pre 的颜色能正确继承。通过修改主题SCSS，然后使用深色主题渲染一个示例Quarto文档来测试，以验证单元格编号是否可见。

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• formatted my issue following the Bug Reports guide

Bug description

In dark themes, the cell number (e.g. In [1]:, In [2]:, ...) from an embedded code cell ends up very dark on a dark background and fails contrast minimums.

These cell numbers are a bare <pre> inside a .cell-decorator div (<div class="cell-decorator"><pre>In [2]:</pre></div>) — the <pre> itself has no class, so its text color comes from an unscoped, generic pre rule rather than anything specific to .cell-decorator.

Bootstrap's own pre rule (_reboot.scss#L300) sets color: $pre-color, which defaults to $body-emphasis-color (_variables.scss#L1774-L1775) — a light-mode-oriented near-black. Quarto's own override (_bootstrap-rules.scss#L949-L953) resets background-color to initial (so .cell-decorator's bare <pre> blends into the page) but never resets color, so the hardcoded near-black text is left sitting on whatever background the page inherits.

Bootstrap's own dark themes carry a defensive fix for exactly this: darkly.scss#L184 and cyborg.scss#L192 both set $pre-color: inherit !default;.

Steps to reproduce

---
title: "Repro"
theme: dark.scss
---

{{< embed source.qmd#cell-one >}}

with dark.scss:

/*-- scss:defaults --*/
$body-bg: #151515;
$body-color: #f8f8f8;

/*-- scss:rules --*/

and source.qmd:

---
title: "Source"
---

```{r}
#| label: cell-one
1 + 1
```

quarto render index.qmd

Actual behavior

The compiled theme CSS resolves to:

pre{...color:#000;background-color:#f8f9fa;...}
pre{background-color:initial;padding:initial;border:initial}

.cell-decorator's <pre> ends up with color: #000 on the page's
$body-bg (#151515) — a contrast ratio of ~1.15:1.

Expected behavior

.cell-decorator's <pre> text should meet 4.5:1 contrast against the
theme's own background, the same way Bootswatch's dark themes handle it.

Author workaround (that generated screenshot): add $pre-color: inherit !default; to the theme's
scss:defaults block:

/*-- scss:defaults --*/
$body-bg: #151515;
$body-color: #f8f8f8;
$pre-color: inherit !default;
/*-- scss:rules --*/

Your environment

• IDE: none (CLI render)
• OS: macOS 26.6.2 (build 25G83)

Quarto check output

Quarto 1.11.4
[✓] Checking environment information...
      Quarto cache location: /Users/charlottewickham/Library/Caches/quarto
[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.10.0: OK
      Dart Sass version 1.101.0: OK
      Deno version 2.7.14: OK
      Typst version 0.15.1: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 1.11.4
      Path: /Applications/quarto/bin

[✓] Checking tools....................OK
      TinyTeX: v2026.04
      Chrome Headless Shell: 150.0.7871.115
      VeraPDF: 1.28.2

[✓] Checking LaTeX....................OK
      Using: TinyTex
      Path: /Users/charlottewickham/Library/TinyTeX/bin/universal-darwin
      Version: 2026

[✓] Checking Chrome Headless....................OK
      Using: Chrome Headless Shell installed by Quarto
      Path: /Users/charlottewickham/Library/Application Support/quarto/chrome-headless-shell/chrome-headless-shell-mac-arm64/chrome-headless-shell
      Version: 150.0.7871.115

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

[✓] Checking R installation...........OK
      Version: 4.6.0
      Path: /Library/Frameworks/R.framework/Versions/4.6/Resources
      LibPaths:
        - /Users/charlottewickham/Library/R/arm64/4.6/library
        - /Library/Frameworks/R.framework/Versions/4.6/Resources/library
      knitr: 1.51
      rmarkdown: 2.31

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

[✓] Checking Python 3 installation....OK
      Version: 3.12.2
      Path: /Users/charlottewickham/.pyenv/versions/3.12.2/bin/python3
      Jupyter: 5.9.1
      Kernels: python3

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

[✓] Checking Julia installation...

---

Investigated with AI assistance, grounded in a local clone of quarto-cli
(see CONTRIBUTING.md "Using AI tools to investigate").