fix(markup): wrap indented code blocks for the code-copy button (#37748)

Indented (4-space) code blocks were emitted by goldmark's default
renderer as plain `<pre><code>` without the `code-block-container`
wrapper that the JS `initMarkupCodeCopy` keys on. As a result, only
fenced code blocks received the copy button. Register
`ast.KindCodeBlock` with a renderer that produces the same wrapper as
the highlighting renderer so both syntaxes get the button.

Extends `TestMarkdownFencedCodeBlock` to assert the wrapper is emitted
for indented blocks (and that HTML inside is escaped).

Co-authored-by: Claude (Opus 4.7) <noreply@anthropic.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/markup/markdown/goldmark.go

@@ -119,12 +119,33 @@ func (r *HTMLRenderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
 	reg.Register(KindDetails, r.renderDetails)
 	reg.Register(KindSummary, r.renderSummary)
 	reg.Register(ast.KindCodeSpan, r.renderCodeSpan)
+	reg.Register(ast.KindCodeBlock, r.renderCodeBlock)
 	reg.Register(KindAttention, r.renderAttention)
 	reg.Register(KindTaskCheckBoxListItem, r.renderTaskCheckBoxListItem)
 	reg.Register(east.KindTaskCheckBox, r.renderTaskCheckBox)
 	reg.Register(KindRawHTML, r.renderRawHTML)
 }
 
+// renderCodeBlock wraps indented code blocks like the fenced renderer
+func (r *HTMLRenderer) renderCodeBlock(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
+	if entering {
+		opening := r.renderInternal.ProtectSafeAttrs(`<div class="code-block-container code-overflow-scroll"><pre class="code-block"><code>`)
+		if _, err := w.WriteString(string(opening)); err != nil {
+			return ast.WalkStop, err
+		}
+		lines := n.Lines()
+		for i := 0; i < lines.Len(); i++ {
+			line := lines.At(i)
+			r.Writer.RawWrite(w, line.Value(source))
+		}
+	} else {
+		if _, err := w.WriteString("</code></pre></div>"); err != nil {
+			return ast.WalkStop, err
+		}
+	}
+	return ast.WalkContinue, nil
+}
+
 func (r *HTMLRenderer) renderDocument(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
 	n := node.(*ast.Document)
 

modules/markup/markdown/markdown_test.go

@@ -601,7 +601,7 @@ func TestMarkdownUlDir(t *testing.T) {
 `, string(result))
 }
 
-func TestMarkdownFencedCodeBlock(t *testing.T) {
+func TestMarkdownCodeBlock(t *testing.T) {
 	testRender := func(input, expected string) {
 		buffer, err := markdown.RenderString(markup.NewTestRenderContext(), input)
 		assert.NoError(t, err)
@@ -618,4 +618,6 @@ func TestMarkdownFencedCodeBlock(t *testing.T) {
 	testRender("```js:app.ts\ncode\n```", jsCommon)
 	testRender("```js,ignore\ncode\n```", jsCommon)
 	testRender("```js ignore\ncode\n```", jsCommon)
+	testRender("    code\n", prefix+`<code>code`+nl+`</code>`+suffix)
+	testRender("    <script>alert(1)</script>\n", prefix+`<code>&lt;script&gt;alert(1)&lt;/script&gt;`+nl+`</code>`+suffix)
 }