Decouple core evaluator from web platform, extract libraries

The core evaluator (spec/evaluator.sx) is now the irreducible computational
core with zero web, rendering, or type-system knowledge. 2531 → 2313 lines.

- Add extensible special form registry (*custom-special-forms* + register-special-form!)
- Add render dispatch hooks (*render-check* / *render-fn*) replacing hardcoded render-active?/is-render-expr?/render-expr
- Extract freeze scopes → spec/freeze.sx (library, not core)
- Extract content addressing → spec/content.sx (library, not core)
- Move sf-deftype/sf-defeffect → spec/types.sx (self-registering)
- Move sf-defstyle → web/forms.sx (self-registering with all web forms)
- Move web tests (defpage, streaming) → web/tests/test-forms.sx
- Add is-else-clause? helper (replaces 5 inline patterns)
- Make escape-html/escape-attr library functions in render.sx (pure SX, not platform-provided)
- Add foundations plan: Step 3.5 (data representations), Step 3.7 (verified components), OCaml for Step 4d
- Update all three bootstrappers (JS 957/957, Python 744/744, OCaml 952/952)

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

hosts/python/bootstrap.py

@@ -179,6 +179,11 @@ class PyEmitter:
             "*batch-depth*": "_batch_depth",
             "*batch-queue*": "_batch_queue",
             "*store-registry*": "_store_registry",
+            "*custom-special-forms*": "_custom_special_forms",
+            "*render-check*": "_render_check",
+            "*render-fn*": "_render_fn",
+            "register-special-form!": "register_special_form_b",
+            "is-else-clause?": "is_else_clause_p",
             "def-store": "def_store",
             "use-store": "use_store",
             "clear-stores": "clear_stores",

hosts/python/platform.py

@@ -612,13 +612,7 @@ def inspect(x):
     return repr(x)
 
 
-def escape_html(s):
-    s = str(s)
-    return s.replace("&", "&amp;").replace("<", "&lt;").replace(">", "&gt;").replace('"', "&quot;")
-
-
-def escape_attr(s):
-    return escape_html(s)
+# escape_html and escape_attr are now library functions defined in render.sx
 
 
 def raw_html_content(x):
@@ -842,7 +836,7 @@ def _sx_parse_int(v, default=0):
     "stdlib.text": '''
 # stdlib.text
 PRIMITIVES["pluralize"] = lambda n, s="", p="s": s if n == 1 else p
-PRIMITIVES["escape"] = escape_html
+PRIMITIVES["escape"] = lambda s: str(s).replace("&", "&amp;").replace("<", "&lt;").replace(">", "&gt;").replace('"', "&quot;")
 PRIMITIVES["strip-tags"] = lambda s: _strip_tags(str(s))
 
 import re as _re
@@ -1647,12 +1641,15 @@ SPEC_MODULES = {
     "signals": ("signals.sx", "signals (reactive signal runtime)"),
     "page-helpers": ("page-helpers.sx", "page-helpers (pure data transformation helpers)"),
     "types": ("types.sx", "types (gradual type system)"),
+    "freeze": ("freeze.sx", "freeze (serializable state boundaries)"),
+    "content": ("content.sx", "content (content-addressed computation)"),
 }
 # Note: frames and cek are now part of evaluator.sx (always loaded as core)
 
 # Explicit ordering for spec modules with dependencies.
+# freeze depends on signals; content depends on freeze.
 SPEC_MODULE_ORDER = [
-    "deps", "engine", "page-helpers", "router", "signals", "types",
+    "deps", "engine", "page-helpers", "router", "signals", "types", "freeze", "content",
 ]
 
 EXTENSION_NAMES = {"continuations"}

hosts/python/tests/run_cek_tests.py

@@ -172,9 +172,6 @@ env["sf-lambda"] = sx_ref.sf_lambda
 env["sf-defcomp"] = sx_ref.sf_defcomp
 env["sf-defisland"] = sx_ref.sf_defisland
 env["sf-defmacro"] = sx_ref.sf_defmacro
-env["sf-defstyle"] = sx_ref.sf_defstyle
-env["sf-deftype"] = sx_ref.sf_deftype
-env["sf-defeffect"] = sx_ref.sf_defeffect
 env["sf-letrec"] = sx_ref.sf_letrec
 env["sf-named-let"] = sx_ref.sf_named_let
 env["sf-dynamic-wind"] = sx_ref.sf_dynamic_wind
@@ -194,10 +191,25 @@ env["ho-every"] = sx_ref.ho_every
 env["ho-for-each"] = sx_ref.ho_for_each
 env["call-fn"] = sx_ref.call_fn
 
-# Render-related (stub for testing — no active rendering)
-env["render-active?"] = lambda: False
-env["is-render-expr?"] = lambda expr: False
-env["render-expr"] = lambda expr, env: NIL
+# Render dispatch globals — evaluator checks *render-check* and *render-fn*
+env["*render-check*"] = NIL
+env["*render-fn*"] = NIL
+
+# Custom special forms registry — modules register forms at load time
+env["*custom-special-forms*"] = {}
+def _register_special_form(name, handler):
+    env["*custom-special-forms*"][name] = handler
+    return NIL
+env["register-special-form!"] = _register_special_form
+
+# is-else-clause? — check if a cond/case test is an else marker
+def _is_else_clause(test):
+    if isinstance(test, Keyword) and test.name == "else":
+        return True
+    if isinstance(test, Symbol) and test.name in ("else", ":else"):
+        return True
+    return False
+env["is-else-clause?"] = _is_else_clause
 
 # Scope primitives
 env["scope-push!"] = sx_ref.PRIMITIVES.get("scope-push!", lambda *a: NIL)
@@ -214,15 +226,12 @@ env["call-thunk"] = lambda f, e: f() if callable(f) else trampoline(eval_expr([f
 # Mutation helpers used by parse-keyword-args etc
 env["dict-get"] = lambda d, k: d.get(k, NIL) if isinstance(d, dict) else NIL
 
-# defhandler, defpage, defquery, defaction — these are registrations
-# Use the bootstrapped versions if they exist, otherwise stub
-for name in ["sf-defhandler", "sf-defpage", "sf-defquery", "sf-defaction"]:
-    pyname = name.replace("-", "_")
-    fn = getattr(sx_ref, pyname, None)
-    if fn:
-        env[name] = fn
-    else:
-        env[name] = lambda args, e, _n=name: NIL
+# defstyle, defhandler, defpage, defquery, defaction — now registered via
+# register-special-form! by forms.sx at load time. Stub them here in case
+# forms.sx is not loaded (CEK tests don't load it).
+for form_name in ["defstyle", "defhandler", "defpage", "defquery", "defaction"]:
+    if form_name not in env["*custom-special-forms*"]:
+        env["*custom-special-forms*"][form_name] = lambda args, e, _n=form_name: NIL
 
 # Load test framework
 with open(os.path.join(_SPEC_TESTS, "test-framework.sx")) as f:

hosts/python/tests/run_tests.py

@@ -248,9 +248,26 @@ env["macro-closure"] = lambda m: m.closure
 env["symbol-name"] = lambda s: s.name if isinstance(s, Symbol) else str(s)
 env["keyword-name"] = lambda k: k.name if isinstance(k, Keyword) else str(k)
 env["sx-serialize"] = sx_ref.sx_serialize if hasattr(sx_ref, "sx_serialize") else lambda x: str(x)
-env["is-render-expr?"] = lambda expr: False
-env["render-active?"] = lambda: False
-env["render-expr"] = lambda expr, env: NIL
+
+# Render dispatch globals — evaluator checks *render-check* and *render-fn*
+env["*render-check*"] = NIL
+env["*render-fn*"] = NIL
+
+# Custom special forms registry — modules register forms at load time
+env["*custom-special-forms*"] = {}
+def _register_special_form(name, handler):
+    env["*custom-special-forms*"][name] = handler
+    return NIL
+env["register-special-form!"] = _register_special_form
+
+# is-else-clause? — check if a cond/case test is an else marker
+def _is_else_clause(test):
+    if isinstance(test, Keyword) and test.name == "else":
+        return True
+    if isinstance(test, Symbol) and test.name in ("else", ":else"):
+        return True
+    return False
+env["is-else-clause?"] = _is_else_clause
 
 # Strict mode stubs (not yet bootstrapped to Python — no-ops for now)
 env["set-strict!"] = lambda val: NIL

hosts/python/transpiler.sx

@@ -93,6 +93,11 @@
   "*batch-depth*" "_batch_depth"
   "*batch-queue*" "_batch_queue"
   "*store-registry*" "_store_registry"
+  "*custom-special-forms*" "_custom_special_forms"
+  "*render-check*" "_render_check"
+  "*render-fn*" "_render_fn"
+  "register-special-form!" "register_special_form_b"
+  "is-else-clause?" "is_else_clause_p"
   "def-store" "def_store"
   "use-store" "use_store"
   "clear-stores" "clear_stores"