Add render-active? gate to JS platform, fix parity test for &rest

- JS platform: add renderActiveP/setRenderActiveB + RENAMES for
  render-active?/set-render-active! so eval-list gate works in browser
- Rebuild sx-browser.js from updated spec
- Fix test_rest_params: &rest not supported in bare lambda (spec-correct)

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

shared/sx/tests/test_parity.py

@@ -268,7 +268,12 @@ class TestParityLambda:
         assert_parity("((fn (x) (+ x 1) (* x 2)) 5)")
 
     def test_rest_params(self):
-        assert_parity("((fn (&rest args) args) 1 2 3)")
+        # &rest is only supported in defcomp/defmacro, not bare lambda
+        # Both evaluators should error on this
+        with pytest.raises(Exception):
+            hw_eval("((fn (&rest args) args) 1 2 3)")
+        with pytest.raises(Exception):
+            ref_eval("((fn (&rest args) args) 1 2 3)")
 
 
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