OCaml bootstrapper Phase 2: HTML renderer, SX server, Python bridge

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

docker-compose.dev-sx.yml

@@ -13,6 +13,8 @@ services:
       ENVIRONMENT: development
       RELOAD: "true"
       SX_USE_REF: "1"
+      SX_USE_OCAML: "1"
+      SX_OCAML_BIN: "/app/bin/sx_server"
       SX_BOUNDARY_STRICT: "1"
       SX_DEV: "1"
     volumes:
@@ -26,6 +28,8 @@ services:
       - ./sx/sx:/app/sx
       - ./sx/path_setup.py:/app/path_setup.py
       - ./sx/entrypoint.sh:/usr/local/bin/entrypoint.sh
+      # OCaml SX kernel binary (built with: cd hosts/ocaml && eval $(opam env) && dune build)
+      - ./hosts/ocaml/_build/default/bin/sx_server.exe:/app/bin/sx_server:ro
       - ./sx/__init__.py:/app/__init__.py:ro
       # sibling models for cross-domain SQLAlchemy imports
       - ./blog/__init__.py:/app/blog/__init__.py:ro