fix: propagate fig-alt on static images to Typst image alt text

The Typst Image handler only checked the `alt` attribute, missing
Quarto's `fig-alt` attribute on static (non-computed) images. This
mirrors the existing fig-alt handling in quarto-post/html.lua.

Closes #14108

Author: gordonwoodhull

src/resources/filters/quarto-post/typst.lua

@@ -227,7 +227,11 @@ function render_typst_fixups()
 
       -- Workaround for Pandoc not passing alt text to Typst image() calls
       -- See: https://github.com/jgm/pandoc/pull/11394
-      local alt_text = image.attributes["alt"]
+      -- Check fig-alt first (Quarto's custom alt text override), then alt, then caption
+      local alt_text = image.attributes[kFigAlt] or image.attributes["alt"]
+      if alt_text then
+        image.attributes[kFigAlt] = nil
+      end
       if (alt_text == nil or alt_text == "") and #image.caption > 0 then
         alt_text = pandoc.utils.stringify(image.caption)
       end

tests/docs/smoke-all/pdf-standard/typst-fig-alt-static-images-img.svg

@@ -0,0 +1,24 @@
+---
+title: "Typst fig-alt propagation for static images"
+format:
+  typst:
+    keep-typ: true
+_quarto:
+  tests:
+    typst:
+      noErrors: default
+      ensureTypstFileRegexMatches:
+        - # Patterns that MUST be found - fig-alt propagated to image(alt: ...)
+          - 'alt:\s*"Alt for captioned non-crossref image"'
+          - 'alt:\s*"Alt for uncaptioned image"'
+        - # Patterns that must NOT be found
+          []
+---
+
+## Static image with caption but no cross-ref label
+
+![A caption](typst-fig-alt-static-images-img.svg){fig-alt="Alt for captioned non-crossref image"}
+
+## Static image without caption and no cross-ref label
+
+![](typst-fig-alt-static-images-img.svg){fig-alt="Alt for uncaptioned image"}