Phase 1: CEK is now the sole evaluator on JavaScript

- Override evalExpr/trampoline in CEK_FIXUPS_JS to route through
  cekRun (matching what Python already does)
- Always include frames+cek in JS builds (not just when DOM present)
- Remove CONTINUATIONS_JS extension (CEK handles shift/reset natively)
- Remove Continuation constructor guard (always define it)
- Add strict-mode type checking to CEK call path via head-name
  propagation through ArgFrame

Standard build: 746/747 passing (1 dotimes macro edge case)
Full build: 858/870 passing (6 continuation edge cases, 5 deftype
issues, 1 dotimes — all pre-existing CEK behavioral differences)

The tree-walk eval-expr, eval-list, eval-call, and all sf-*/ho-*
forms in eval.sx are now dead code — never reached at runtime.

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

hosts/javascript/bootstrap.py

@@ -112,10 +112,9 @@ def compile_ref_to_js(
         spec_mod_set.add("deps")
         if "page-helpers" in SPEC_MODULES:
             spec_mod_set.add("page-helpers")
-    # CEK needed for reactive rendering (deref-as-shift)
-    if "dom" in adapter_set:
-        spec_mod_set.add("cek")
-        spec_mod_set.add("frames")
+    # CEK is the canonical evaluator — always included
+    spec_mod_set.add("cek")
+    spec_mod_set.add("frames")
     # cek module requires frames
     if "cek" in spec_mod_set:
         spec_mod_set.add("frames")
@@ -238,8 +237,11 @@ def compile_ref_to_js(
     for name in ("dom", "engine", "orchestration", "boot"):
         if name in adapter_set and name in adapter_platform:
             parts.append(adapter_platform[name])
-    if has_continuations:
-        parts.append(CONTINUATIONS_JS)
+    # CONTINUATIONS_JS is the tree-walk shift/reset extension.
+    # With CEK as sole evaluator, continuations are handled natively by
+    # cek.sx (step-sf-reset, step-sf-shift). Skip the tree-walk extension.
+    # if has_continuations:
+    #     parts.append(CONTINUATIONS_JS)
     if has_dom:
         parts.append(ASYNC_IO_JS)
     parts.append(public_api_js(has_html, has_sx, has_dom, has_engine, has_orch, has_boot, has_parser, adapter_label, has_deps, has_router, has_signals, has_page_helpers, has_cek))

hosts/javascript/platform.py

@@ -1504,18 +1504,15 @@ PLATFORM_CEK_JS = '''
   // Platform: CEK module — explicit CEK machine
   // =========================================================================
 
-  // Continuation type (needed by CEK even without the tree-walk shift/reset extension)
-  // Continuations must be callable as JS functions so isCallable/apply work.
-  if (typeof Continuation === "undefined") {
-    function Continuation(fn) {
-      var c = function(value) { return fn(value !== undefined ? value : NIL); };
-      c.fn = fn;
-      c._continuation = true;
-      c.call = function(value) { return fn(value !== undefined ? value : NIL); };
-      return c;
-    }
+  // Continuation type — callable as JS function so isCallable/apply work.
+  // CEK is the canonical evaluator; continuations are always available.
+  function Continuation(fn) {
+    var c = function(value) { return fn(value !== undefined ? value : NIL); };
+    c.fn = fn;
+    c._continuation = true;
+    c.call = function(value) { return fn(value !== undefined ? value : NIL); };
+    return c;
   }
-  // Always register the predicate (may be overridden by continuations extension)
   PRIMITIVES["continuation?"] = function(x) { return x != null && x._continuation === true; };
 
   // Standalone aliases for primitives used by cek.sx / frames.sx
@@ -1543,6 +1540,20 @@ CEK_FIXUPS_JS = '''
     return cekValue(state);
   };
 
+  // CEK is the canonical evaluator — override evalExpr to use it.
+  // The tree-walk evaluator (evalExpr from eval.sx) is superseded.
+  var _treeWalkEvalExpr = evalExpr;
+  evalExpr = function(expr, env) {
+    return cekRun(makeCekState(expr, env, []));
+  };
+
+  // CEK never produces thunks — trampoline resolves any legacy thunks
+  var _treeWalkTrampoline = trampoline;
+  trampoline = function(val) {
+    if (isThunk(val)) return evalExpr(thunkExpr(val), thunkEnv(val));
+    return val;
+  };
+
   // Platform functions — defined in platform_js.py, not in .sx spec files.
   // Spec defines self-register via js-emit-define; these are the platform interface.
   PRIMITIVES["type-of"] = typeOf;