fig-alt doesn't propogate to LaTeX non-float images

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

When rendering to .pdf with pdf-standard: ua-2, the alt-text is not included in the .tex file, whereas when rendering to .html, it is included.

Steps to reproduce

---
title: "accessibility test"
format:
  pdf:
    keep-tex: true
    pdf-standard: ua-2
    lang: en
  html:
    embed-resources: true
    html-math-method:
      method: mathjax
      url: "https://cdn.jsdelivr.net/npm/mathjax@4.1/tex-mml-chtml.js"
---

A plot of $X$ vs. $X^2$:

```{r}
#| fig-alt: "scatterplot of X vs. X^2"
#| echo: false
#| warning: false

library(ggplot2)

X <- rnorm(5)
ggplot(NULL, aes(x=X, y=X^2)) + geom_point()
```

Actual behavior

The relevant line in the .tex file:

\pandocbounded{\includegraphics[keepaspectratio]{test_files/figure-pdf/unnamed-chunk-1-1.pdf}}

The relevant lines in the .html file (image id edited):

<figure class="figure">
<p><img role="img" aria-label="scatterplot of X vs. X^2" src="data:image/png;base64,..." class="img-fluid figure-img" alt="scatterplot of X vs. X^2" width="672"></p>
</figure>

Expected behavior

The .tex should read:

\pandocbounded{\includegraphics[alt={scatterplot of X vs. X^2}, keepaspectratio]{test_files/figure-pdf/unnamed-chunk-1-1.pdf}}

Your environment

IDE: RStudio 2026.01.1+403
OS: Windows 11 Pro 24H2

Quarto check output

C:\Users>quarto check
Quarto 1.9.36
[>] Checking environment information...
      Quarto cache location: C:\Users\***\***\Local\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: 1.9.36
      Path: C:\Program Files\Quarto\bin
      CodePage: 1252

[>] Checking tools....................OK
      TinyTeX: v2026.03.02
      Chromium: (not installed)
      Chrome Headless Shell: (not installed)
      VeraPDF: (not installed)

[>] Checking LaTeX....................OK
      Using: TinyTex
      Path: C:\Users\***\AppData\Roaming\TinyTeX\bin\windows\
      Version: 2026

[>] 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 R installation...........OK
      Version: 4.4.3
      Path: C:/PROGRA~1/R/R-44~1.3
      LibPaths:
        - C:/R/Library
        - C:/Program Files/R/R-4.4.3/library
      knitr: 1.51
      rmarkdown: 2.27

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

[>] Checking Python 3 installation....OK
      Version: 3.10.6
      Path: C:/Users/***/AppData/Local/Programs/Python/Python310/python.exe
      Jupyter: (None)

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

[>] Checking Julia installation...

Use the supplied Quarto document with the R figure as the reproduction entry point, then compare the generated .tex and HTML outputs under pdf-standard: ua-2. Trace the non-float image rendering path and verify that the completed .tex includes the figure's alt text while HTML behavior remains unchanged.