feat: extract soul-demo into standalone Cloud Run service

Dockerfile.stage

@@ -1,16 +1,14 @@
-# Dockerfile.stage — Stage build: landing server + soul-demo in one image.
+# Dockerfile.stage — Stage build: landing server only.
 #
-# Both processes run in the same container:
-#   - neuron-web  on port 8080 (landing page server)
-#   - soul-demo   on port 7772 (demo chat, localhost only)
+# neuron-web runs on port 8080 (landing page server).
+# soul-demo is now a separate Cloud Run service (soul-demo-stage).
 #
-# All binaries (neuron-web, soul-demo) are pre-built by CI on the host runner
-# before this Dockerfile runs. This keeps the Docker build single-stage with
-# no compilation and no network downloads.
+# neuron-web binary is pre-built by CI on the host runner before this
+# Dockerfile runs. This keeps the Docker build single-stage with no
+# compilation and no network downloads.
 #
 # CI pre-build steps (in stage.yaml):
 #   - neuron-web: built by `elb build` → dist/neuron-landing
-#   - soul-demo:  compiled by cc on host → dist/soul-demo
 
 FROM ubuntu:24.04
 
@@ -24,20 +22,12 @@ RUN apt-get update \
  && rm -rf /var/lib/apt/lists/* \
  && groupadd -r landing && useradd -r -g landing landing \
  && mkdir -p /srv/landing/assets /srv/landing/js /srv/landing/shares \
- && mkdir -p /srv/soul/engram-demo \
- && chown -R landing:landing /srv/landing /srv/soul
+ && chown -R landing:landing /srv/landing
 
 # neuron-web binary — produced by `elb build` in CI (linux/amd64)
 COPY dist/neuron-landing /usr/local/bin/neuron-web
 RUN chmod +x /usr/local/bin/neuron-web
 
-# soul-demo binary — compiled by cc on host runner in CI
-COPY dist/soul-demo /usr/local/bin/soul-demo
-RUN chmod +x /usr/local/bin/soul-demo
-
-# Engram snapshot — baked in so soul has memory from cold start
-COPY dist/engram-snapshot.json /srv/soul/engram-demo/snapshot.json
-
 COPY src/assets /srv/landing/assets
 COPY dist/js    /srv/landing/js
 COPY src/llms.txt /srv/landing/llms.txt
@@ -55,8 +45,6 @@ RUN chmod +x /usr/local/bin/entrypoint.sh
 
 ENV LANDING_ROOT=/srv/landing
 ENV PORT=8080
-ENV NEURON_HOME=/srv/soul/engram-demo
-ENV NEURON_PORT=7772
 
 EXPOSE 8080