Add 68 new tests: continuations-advanced + render-advanced (938/938)

test-continuations-advanced.sx (41 tests):
  multi-shot continuations, composition, provide/context basics,
  provide across shift, scope/emit basics, scope across shift

test-render-advanced.sx (27 tests):
  nested components, dynamic content, list patterns,
  component patterns, special elements

Bugs found and documented:
- case in render context returns DOM object (CEK dispatches case
  before HTML adapter sees it — use cond instead for render)
- context not visible in shift body (correct: shift body runs
  outside the reset/provide boundary)
- Multiple shifts consume reset (correct: each shift needs its own
  reset)

Python runner: skip test-continuations-advanced.sx without --full.

JS 815/815 standard, 938/938 full, Python 706/706.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

shared/static/scripts/sx-browser.js

@@ -14,7 +14,7 @@
   // =========================================================================
 
   var NIL = Object.freeze({ _nil: true, toString: function() { return "nil"; } });
-  var SX_VERSION = "2026-03-15T15:05:23Z";
+  var SX_VERSION = "2026-03-15T15:31:20Z";
 
   function isNil(x) { return x === NIL || x === null || x === undefined; }
   function isSxTruthy(x) { return x !== false && !isNil(x); }