Use dom-on for event handlers; add CI config and stepper Playwright test

- web/orchestration.sx, web/signals.sx: dom-listen → dom-on (trampoline
  wrapper that resolves TCO thunks from Lambda event handlers)
- .gitea/: CI workflow and Dockerfile for automated test runs
- tests/playwright/stepper.spec.js: stepper widget smoke test
- Remove stale artdag .pyc file

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

.gitea/Dockerfile.test

@@ -0,0 +1,84 @@
+# syntax=docker/dockerfile:1
+#
+# CI test image — Python 3 + Node.js + OCaml 5.2 + dune.
+#
+# Build chain:
+#   1. Compile OCaml from checked-in sx_ref.ml  — produces sx_server.exe
+#   2. Bootstrap JS (sx-browser.js)             — OcamlSync transpiler → JS
+#   3. Re-bootstrap OCaml (sx_ref.ml)           — OcamlSync transpiler → OCaml
+#   4. Recompile OCaml with fresh sx_ref.ml     — final native binary
+#
+# Test suites (run at CMD):
+#   - JS standard + full tests         — Node
+#   - OCaml spec tests                 — native binary
+#   - OCaml bridge integration tests   — Python + OCaml subprocess
+#
+# Usage:
+#   docker build -f .gitea/Dockerfile.test -t sx-test .
+#   docker run --rm sx-test
+
+FROM ocaml/opam:debian-12-ocaml-5.2
+
+USER root
+RUN apt-get update && apt-get install -y --no-install-recommends \
+      python3 ca-certificates curl xz-utils \
+    && rm -rf /var/lib/apt/lists/*
+# Node.js — direct binary (avoids the massive Debian nodejs dep tree)
+RUN NODE_VERSION=22.22.1 \
+    && ARCH=$(dpkg --print-architecture | sed 's/amd64/x64/;s/arm64/arm64/;s/armhf/armv7l/') \
+    && curl -fsSL "https://nodejs.org/dist/v${NODE_VERSION}/node-v${NODE_VERSION}-linux-${ARCH}.tar.xz" \
+       | tar -xJ --strip-components=1 -C /usr/local
+USER opam
+
+# Install dune into the opam switch
+RUN opam install dune -y
+
+# Bake the opam switch PATH into the image so dune/ocamlfind work in RUN
+ENV PATH="/home/opam/.opam/5.2/bin:${PATH}"
+
+WORKDIR /home/opam/project
+
+# Copy OCaml sources first (changes less often → better caching)
+COPY --chown=opam:opam hosts/ocaml/dune-project ./hosts/ocaml/
+COPY --chown=opam:opam hosts/ocaml/lib/         ./hosts/ocaml/lib/
+COPY --chown=opam:opam hosts/ocaml/bin/         ./hosts/ocaml/bin/
+
+# Copy spec, web, shared (needed by bootstrappers + tests)
+COPY --chown=opam:opam spec/           ./spec/
+COPY --chown=opam:opam web/            ./web/
+COPY --chown=opam:opam shared/sx/      ./shared/sx/
+COPY --chown=opam:opam shared/__init__.py ./shared/__init__.py
+
+# Copy JS host (bootstrapper + test runner)
+COPY --chown=opam:opam hosts/javascript/ ./hosts/javascript/
+
+# Copy OCaml host (bootstrapper + transpiler)
+COPY --chown=opam:opam hosts/ocaml/bootstrap.py   ./hosts/ocaml/bootstrap.py
+COPY --chown=opam:opam hosts/ocaml/transpiler.sx   ./hosts/ocaml/transpiler.sx
+
+# Create output directory for JS builds
+RUN mkdir -p shared/static/scripts
+
+# Step 1: Compile OCaml from checked-in sx_ref.ml
+#   → produces sx_server.exe (needed by both JS and OCaml bootstrappers)
+RUN cd hosts/ocaml && dune build
+
+# Step 2: Bootstrap JS (uses sx_server.exe via OcamlSync)
+RUN python3 hosts/javascript/cli.py \
+      --output shared/static/scripts/sx-browser.js \
+    && python3 hosts/javascript/cli.py \
+      --extensions continuations --spec-modules types \
+      --output shared/static/scripts/sx-full-test.js
+
+# Step 3: Re-bootstrap OCaml (transpile current spec → fresh sx_ref.ml)
+RUN python3 hosts/ocaml/bootstrap.py \
+      --output hosts/ocaml/lib/sx_ref.ml
+
+# Step 4: Recompile OCaml with freshly bootstrapped sx_ref.ml
+RUN cd hosts/ocaml && dune build
+
+# Default: run all tests
+COPY --chown=opam:opam .gitea/run-ci-tests.sh ./run-ci-tests.sh
+RUN chmod +x run-ci-tests.sh
+
+CMD ["./run-ci-tests.sh"]