Keep KOMA classes working with pdf-standard under KOMA-Script 3.49.3 (#15154)

KOMA-Script 3.49.3 turns the \DocumentMetadata check into a fatal error
for scrartcl, scrreprt and scrbook without tagging support, so every
pdf-standard PDF render failed once TeX Live shipped the new release.
Quarto now defines KOMA's documented replacement hook
\komascript_documentmetadata_test: as a no-op after \DocumentMetadata,
restoring the 3.49.2 behaviour with no change to class or layout.
Non-KOMA classes never read the macro.

- Define the no-op hook in the pdf-standard template, guarded so an
  existing definition is kept
- Leave document-metadata.latex unchanged so it still matches Pandoc's
  partial

See #14422 for KOMA classes not tagging sectioning commands.

Fixes #15143

Author: cderv

news/changelog-1.11.md

@@ -8,6 +8,7 @@ All changes included in 1.11:
 - ([#14857](https://github.com/quarto-dev/quarto-cli/issues/14857)): Fix `quarto install chrome-headless-shell` (and `quarto install chromium`) failing with a 404 on Linux arm64 due to a stale Playwright CDN URL.
 - ([#14946](https://github.com/quarto-dev/quarto-cli/issues/14946)): Fix `revealjs` and `dashboard` logos resolving to broken paths in documents in a project subdirectory when the project has a brand (regression introduced in v1.8.22). Logo paths are now always relative to the document; a project-relative logo path in a website with a brand still works but prints a deprecation warning.
 - ([#14993](https://github.com/quarto-dev/quarto-cli/issues/14993)): Fix Typst output dropping a brand font from a `font-family` list when another document in the same directory or project was rendered first with different brand fonts.
+- ([#15143](https://github.com/quarto-dev/quarto-cli/issues/15143)): Fix PDF rendering with `pdf-standard` failing with `\DocumentMetadata not supported!` after updating to KOMA-Script 3.49.3, which provides the default document classes.
 
 ## Dependencies
 

src/resources/formats/pdf/pandoc/template.tex

@@ -1,4 +1,12 @@
 $document-metadata.latex()$
+$if(pdfstandard)$
+$-- KOMA-Script 3.49.3 aborts on \DocumentMetadata unless \komascript_documentmetadata_test: exists;
+$-- a no-op keeps the 3.49.2 behaviour (#15143). The guard keeps a definition made earlier.
+\ExplSyntaxOn
+\cs_if_exist:NF \komascript_documentmetadata_test:
+  { \cs_new:Npn \komascript_documentmetadata_test: { } }
+\ExplSyntaxOff
+$endif$
 % Options for packages loaded elsewhere
 $passoptions.latex()$
 %