Fix renderDOM swallowing pre-rendered DOM nodes as empty dicts

renderComponentDOM now eagerly renders kwarg values that are render
expressions (HTML tags, <>, ~components) into DOM nodes. But renderDOM
treated any non-array object as a dict and returned an empty fragment,
silently discarding pre-rendered content. Add a nodeType check to pass
DOM nodes through unchanged.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shared/static/scripts/sx.js

@@ -691,6 +691,9 @@
     // Keyword → text
     if (isKw(expr)) return document.createTextNode(expr.name);
 
+    // Pre-rendered DOM node → return as-is
+    if (expr && expr.nodeType) return expr;
+
     // Dict → empty
     if (expr && typeof expr === "object" && !Array.isArray(expr)) return document.createDocumentFragment();