Fix filter/map tag disambiguation inside SVG context without keyword attrs

(filter (feTurbulence ...)) inside (svg ...) has no keyword first arg,
so the keyword-only check dispatched it as a HO function. Now also
check SVG/MathML context (ns in client, _svg_context in server).

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

shared/static/scripts/sx.js

@@ -1288,9 +1288,9 @@
       if (name.indexOf("html:") === 0) return renderElement(name.substring(5), expr.slice(1), env, ns);
 
       // Render-aware special forms
-      // If name is also an HTML tag and first arg is Keyword → tag call
+      // If name is also an HTML tag and (keyword arg or SVG/MathML ns) → tag call
       if (RENDER_FORMS[name]) {
-        if (HTML_TAGS[name] && expr.length > 1 && isKw(expr[1])) return renderElement(name, expr.slice(1), env, ns);
+        if (HTML_TAGS[name] && ((expr.length > 1 && isKw(expr[1])) || ns)) return renderElement(name, expr.slice(1), env, ns);
         return RENDER_FORMS[name](expr, env, ns);
       }