Add CEK Machine section under Geography with live island demos

geography/cek.sx: overview page (three registers, deref-as-shift
explanation) + demo page with 5 live islands (counter, computed chain,
reactive attrs, stopwatch effect+cleanup, batch coalescing). Nav entry,
router routes, defpage definitions. CEK exports (cekRun, makeCekState,
makeReactiveResetFrame, evalExpr) added to Sx public API via
platform_js.py.

Co-Authored-By: Claude Opus 4.6 <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 = "2026-03-14T01:00:32Z";
+  var SX_VERSION = "2026-03-14T01:23:35Z";
 
   function isNil(x) { return x === NIL || x === null || x === undefined; }
   function isSxTruthy(x) { return x !== false && !isNil(x); }
@@ -1391,7 +1391,7 @@ var d2 = hexDigitValue(nth(source, pos));
 var _ = (pos = (pos + 1));
 var d3 = hexDigitValue(nth(source, pos));
 var _ = (pos = (pos + 1));
-buf = (String(buf) + String(charFromCode(((((d0 * 4096) + (d1 * 256)) + (d2 * 16)) + d3))));
+buf = (String(buf) + String(charFromCode((d0 * 4096))));
 continue; } } else { buf = (String(buf) + String((isSxTruthy((esc == "n")) ? "\n" : (isSxTruthy((esc == "t")) ? "\t" : (isSxTruthy((esc == "r")) ? "\r" : esc)))));
 pos = (pos + 1);
 continue; } } } else { buf = (String(buf) + String(ch));
@@ -6442,87 +6442,6 @@ return forEach(function(d) { return invoke(d); }, subDisposers); });
   };
 
 
-  // =========================================================================
-  // Extension: Delimited continuations (shift/reset)
-  // =========================================================================
-
-  function Continuation(fn) { this.fn = fn; }
-  Continuation.prototype._continuation = true;
-  Continuation.prototype.call = function(value) { return this.fn(value !== undefined ? value : NIL); };
-
-  function ShiftSignal(kName, body, env) {
-    this.kName = kName;
-    this.body = body;
-    this.env = env;
-  }
-
-  PRIMITIVES["continuation?"] = function(x) { return x != null && x._continuation === true; };
-
-  var _resetResume = [];
-
-  function sfReset(args, env) {
-    var body = args[0];
-    try {
-      return trampoline(evalExpr(body, env));
-    } catch (e) {
-      if (e instanceof ShiftSignal) {
-        var sig = e;
-        var cont = new Continuation(function(value) {
-          if (value === undefined) value = NIL;
-          _resetResume.push(value);
-          try {
-            return trampoline(evalExpr(body, env));
-          } finally {
-            _resetResume.pop();
-          }
-        });
-        var sigEnv = merge(sig.env);
-        sigEnv[sig.kName] = cont;
-        return trampoline(evalExpr(sig.body, sigEnv));
-      }
-      throw e;
-    }
-  }
-
-  function sfShift(args, env) {
-    if (_resetResume.length > 0) {
-      return _resetResume[_resetResume.length - 1];
-    }
-    var kName = symbolName(args[0]);
-    var body = args[1];
-    throw new ShiftSignal(kName, body, env);
-  }
-
-  // Wrap evalList to intercept reset/shift
-  var _baseEvalList = evalList;
-  evalList = function(expr, env) {
-    var head = expr[0];
-    if (isSym(head)) {
-      var name = head.name;
-      if (name === "reset") return sfReset(expr.slice(1), env);
-      if (name === "shift") return sfShift(expr.slice(1), env);
-    }
-    return _baseEvalList(expr, env);
-  };
-
-  // Wrap aserSpecial to handle reset/shift in SX wire mode
-  if (typeof aserSpecial === "function") {
-    var _baseAserSpecial = aserSpecial;
-    aserSpecial = function(name, expr, env) {
-      if (name === "reset") return sfReset(expr.slice(1), env);
-      if (name === "shift") return sfShift(expr.slice(1), env);
-      return _baseAserSpecial(name, expr, env);
-    };
-  }
-
-  // Wrap typeOf to recognize continuations
-  var _baseTypeOf = typeOf;
-  typeOf = function(x) {
-    if (x != null && x._continuation) return "continuation";
-    return _baseTypeOf(x);
-  };
-
-
   // =========================================================================
   // Async IO: Promise-aware rendering for client-side IO primitives
   // =========================================================================
@@ -7320,6 +7239,14 @@ return forEach(function(d) { return invoke(d); }, subDisposers); });
     context: sxContext,
     emit: sxEmit,
     emitted: sxEmitted,
+    cekRun: cekRun,
+    makeCekState: makeCekState,
+    makeCekValue: makeCekValue,
+    cekStep: cekStep,
+    cekTerminal: cekTerminal_p,
+    cekValue: cekValue,
+    makeReactiveResetFrame: makeReactiveResetFrame,
+    evalExpr: evalExpr,
     _version: "ref-2.0 (boot+dom+engine+html+orchestration+parser+sx, bootstrap-compiled)"
   };