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>

sx/sxc/pages/__init__.py

@@ -21,17 +21,7 @@ def _load_sx_page_files() -> None:
     load_service_components(service_root, service_name="sx")
     load_sx_dir(_sxc_dir)
     watch_sx_dir(_sxc_dir)
-    # Register page helpers as primitives so the CEK machine can find them
-    # during nested async component expansion (e.g. highlight inside ~docs/code
-    # inside a plan component inside ~layouts/doc). Without this, the env_merge
-    # chain loses page helpers because component closures don't capture them.
-    from shared.sx.ref.sx_ref import PRIMITIVES
-    helpers = get_page_helpers("sx")
-    for name, fn in helpers.items():
-        PRIMITIVES[name] = fn
-
-    # helper is registered as an IO primitive in primitives_io.py,
-    # intercepted by async_eval before hitting the CEK machine.
-    import logging; logging.getLogger("sx.pages").info("Injected %d page helpers as primitives: %s", len(helpers), list(helpers.keys())[:5])
+    # Page helpers are accessed via the OCaml IO bridge (helper "name" args...)
+    # — no Python-side PRIMITIVES registration needed.
 
     load_page_dir(os.path.dirname(__file__), "sx")

sx/sxc/pages/sx_router.py

@@ -93,7 +93,7 @@ async def eval_sx_url(raw_path: str) -> Any:
     from shared.sx.helpers import full_page_sx, oob_page_sx, sx_response, sx_page
     from shared.sx.page import get_template_context
     from shared.browser.app.utils.htmx import is_htmx_request
-    from shared.sx.ref.sx_ref import prepare_url_expr
+    from shared.sx.pages import prepare_url_expr
 
     path = unquote(raw_path).strip()