Fix sx_docs Dockerfile: copy integration_tests.ml for dune build

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

sx/Dockerfile

@@ -9,7 +9,8 @@ WORKDIR /home/opam/sx
 COPY --chown=opam:opam hosts/ocaml/dune-project ./
 COPY --chown=opam:opam hosts/ocaml/lib/ ./lib/
 COPY --chown=opam:opam hosts/ocaml/bin/dune hosts/ocaml/bin/run_tests.ml \
-     hosts/ocaml/bin/debug_set.ml hosts/ocaml/bin/sx_server.ml ./bin/
+     hosts/ocaml/bin/debug_set.ml hosts/ocaml/bin/sx_server.ml \
+     hosts/ocaml/bin/integration_tests.ml ./bin/
 RUN dune build bin/sx_server.exe
 
 # --- Stage 2: Python app ---