claude: refactor foo-engine test to use Quarto API

Use breakQuartoMd API for cell iteration instead of raw regex, making
the code more idiomatic and fixing Windows CI failures caused by line
ending differences. Also fix test syntax to use {python .foo}
(space-separated) which is recognized by breakQuartoMd.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: gordonwoodhull

tests/docs/smoke-all/engine/class-override/_extensions/foo-engine/foo-engine.js

@@ -55,26 +55,36 @@ const fooEngineDiscovery = {
       },
 
       execute: async (options) => {
-        // Replace python.foo code blocks with a marker div showing we processed them
-        let markdown = options.target.markdown.value;
-
-        // Find and replace {python.foo} blocks with our marker output
-        const codeBlockRegex = /```\{python\.foo[^}]*\}\n([\s\S]*?)```/g;
-        markdown = markdown.replace(codeBlockRegex, (match, code) => {
-          return `
-::: {#foo-engine-marker .foo-engine-output}
+        const chunks = await quarto.markdownRegex.breakQuartoMd(
+          options.target.markdown,
+        );
+
+        const processedCells = [];
+        for (const cell of chunks.cells) {
+          if (
+            typeof cell.cell_type === "object" &&
+            cell.cell_type.language === "python"
+          ) {
+            const header = cell.sourceVerbatim.value.split(/\r?\n/)[0];
+            const hasClassFoo = /\.foo\b/.test(header);
+            if (hasClassFoo) {
+              processedCells.push(`::: {#foo-engine-marker .foo-engine-output}
 **FOO ENGINE PROCESSED THIS BLOCK**
 
 Original code:
 \`\`\`python
-${code.trim()}
+${cell.source.value.trim()}
 \`\`\`
 :::
-`;
-        });
+`);
+              continue;
+            }
+          }
+          processedCells.push(cell.sourceVerbatim.value);
+        }
 
         return {
-          markdown: markdown,
+          markdown: processedCells.join(""),
           supporting: [],
           filters: [],
         };

tests/docs/smoke-all/engine/class-override/test.qmd

@@ -18,7 +18,7 @@ This document tests that `{python.foo}` blocks are processed by the foo-engine
 instead of Jupyter, because foo-engine claims `python` with `firstClass === "foo"`
 at priority 2 (higher than Jupyter's default of 1).
 
-```{python.foo}
+```{python .foo}
 x = 1 + 1
 print(x)
 ```