Refactor PDF content rendering: improve list indentation logic, add numbered code block rendering with gutter, and update text wrapping alignment.

markdown_parser.go

@@ -119,8 +119,8 @@ func RenderAST(doc ast.Node, content []byte, r *IHKRenderer) error {
 				}
 				// Fall through: render as plain code block on error
 			}
-			// Render non-diagram code blocks as monospace paragraphs
-			r.RenderParagraphSpans([]InlineSpan{{Text: code, Code: true}})
+			// Render as a numbered code block (gutter + monospace body).
+			r.RenderCodeBlock(lang, code)
 			return ast.WalkSkipChildren, nil
 
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