Add clarifying comment for kbd/kdb dual mapping in factory

Agent-Logs-Url: https://github.com/webexpress-framework/WebExpress.WebCore/sessions/17d12c9c-ee3b-4dfb-b579-6b479c2f3a9a

Co-authored-by: ReneSchwarzer <31061438+ReneSchwarzer@users.noreply.github.com>

Author: Copilot

src/WebExpress.WebCore/WebHtml/Parser/HtmlElementFactory.cs

@@ -77,6 +77,9 @@ public class HtmlElementFactory
                 ["dfn"] = () => new HtmlElementTextSemanticsDfn(),
                 ["em"] = () => new HtmlElementTextSemanticsEm(),
                 ["i"] = () => new HtmlElementTextSemanticsI(),
+                // The standard HTML element is <kbd>, but the existing class uses "kdb" as
+                // its element name.  Both spellings are mapped so that the parser handles
+                // real-world HTML (<kbd>) as well as the project's own renderer output (<kdb>).
                 ["kbd"] = () => new HtmlElementTextSemanticsKdb(),
                 ["kdb"] = () => new HtmlElementTextSemanticsKdb(),
                 ["mark"] = () => new HtmlElementTextSemanticsMark(),