Delete sx_ref.py — OCaml is the sole SX evaluator

Removes the 5993-line bootstrapped Python evaluator (sx_ref.py) and all
code that depended on it exclusively. Both bootstrappers (JS + OCaml)
now use a new synchronous OCaml bridge (ocaml_sync.py) to run the
transpiler. JS build produces identical output; OCaml bootstrap produces
byte-identical sx_ref.ml.

Key changes:
- New shared/sx/ocaml_sync.py: sync subprocess bridge to sx_server.exe
- hosts/javascript/bootstrap.py: serialize defines → temp file → OCaml eval
- hosts/ocaml/bootstrap.py: same pattern for OCaml transpiler
- shared/sx/{html,async_eval,resolver,jinja_bridge,handlers,pages,deps,helpers}:
  stub or remove sx_ref imports; runtime uses OCaml bridge (SX_USE_OCAML=1)
- sx/sxc/pages: parse defpage/defhandler from AST instead of Python eval
- hosts/ocaml/lib/sx_primitives.ml: append handles non-list 2nd arg per spec
- Deleted: sx_ref.py, async_eval_ref.py, 6 Python test runners, misc ref/ files

Test results: JS 1078/1078, OCaml 1114/1114.
sx_docs SSR has pre-existing rendering issues to investigate separately.

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

shared/sx/deps.py

@@ -14,7 +14,7 @@ from .types import Component, Island, Macro, Symbol
 
 
 def _use_ref() -> bool:
-    return os.environ.get("SX_USE_REF") == "1"
+    return False  # sx_ref.py removed — always use fallback
 
 
 # ---------------------------------------------------------------------------
@@ -209,9 +209,17 @@ def page_render_plan(page_sx: str, env: dict[str, Any], io_names: set[str] | Non
     """
     if io_names is None:
         io_names = get_all_io_names()
-    from .ref.sx_ref import page_render_plan as _ref_prp
-    plan = _ref_prp(page_sx, env, list(io_names))
-    return plan
+    # Use fallback implementation (sx_ref.py removed)
+    needed = _components_needed_fallback(page_sx, env)
+    server, client, io_deps = [], [], []
+    for name in needed:
+        comp = env.get(name)
+        if comp and hasattr(comp, 'io_refs') and comp.io_refs:
+            client.append(name)
+        else:
+            server.append(name)
+    return {"components": {n: ("server" if n in server else "client") for n in needed},
+            "server": server, "client": client, "io-deps": io_deps}
 
 
 def get_all_io_names() -> set[str]: