fix(ci): isolate imported client test image

Dockerfile

@@ -1,19 +1,24 @@
 # Local-only dedicated-server build and verification image. Pin the Godot
 # release family used by project.godot; no image is pushed by this repository.
-FROM --platform=linux/amd64 barichello/godot-ci:4.7.1 AS exporter
+FROM --platform=linux/amd64 barichello/godot-ci:4.7.1 AS project-imported
 WORKDIR /workspace
 RUN apt-get update \
  && apt-get install -y --no-install-recommends libfontconfig1 \
  && rm -rf /var/lib/apt/lists/*
 COPY Game /workspace/Game
-# The ENet integration workflow runs its multi-process harness inside this
-# pinned Godot image so source and CI use the same engine version.
+RUN godot --headless --editor --path Game --import --quit
+
+# Test the source client from an untouched, fully imported project. The
+# dedicated-server export below rewrites the main scene and must not be used
+# to run client integration tests.
+FROM project-imported AS enet-test
 COPY scripts/verify_enet_integration.sh /workspace/scripts/verify_enet_integration.sh
+
 # Godot dedicated exports disallow command-line scene overrides. Bake the
 # server scene into this export (the interactive project's source stays
 # unchanged), then generate the global-script/autoload metadata it needs.
+FROM project-imported AS exporter
 RUN sed -i 's|^run/main_scene=.*$|run/main_scene="res://scenes/server_boot.tscn"|' Game/project.godot \
- && godot --headless --editor --path Game --import --quit \
  && mkdir -p /opt/cosmic-clash \
  && godot --headless --path Game --export-release "Linux Dedicated Server" /opt/cosmic-clash/CosmicClashServer.x86_64