Fix docker CI build size

.github/workflows/build-image.yml

@@ -9,8 +9,19 @@ jobs:
     steps:
     - uses: actions/checkout@v4
 
+    - name: Free disk space
+      uses: jlumbroso/free-disk-space@main
+      with:
+        tool-cache: false
+        android: true
+        dotnet: true
+        haskell: true
+        large-packages: true
+        docker-images: true
+        swap-storage: true
+
     - name: Build Docker image
       run: docker build -t image -f dockerfiles/Dockerfile .
 
     - name: Run pytest on image
-      run: docker run image poetry run pytest
+      run: docker run image pytest

dockerfiles/Dockerfile

@@ -4,17 +4,16 @@ FROM python:3.13-slim
 # Set the working directory in the container
 WORKDIR /app
 
-# Install poetry
-RUN pip install --no-cache-dir poetry poetry-plugin-export
-
 # Copy the dependency files to the working directory
 COPY pyproject.toml poetry.lock ./
 
-# Using poetry to make a requirements.txt then pip to do the install.
-# Pip is aggressive with storage space.
-RUN poetry export -f requirements.txt -o requirements.txt --without-hashes --with dev
-
-RUN pip install --no-cache-dir -r requirements.txt \
+# Install poetry, export requirements, install deps with CPU-only PyTorch,
+# then clean up poetry -- all in one layer to minimize image size.
+RUN pip install --no-cache-dir poetry poetry-plugin-export \
+    && poetry export -f requirements.txt -o requirements.txt --without-hashes --with dev \
+    && pip install --no-cache-dir -r requirements.txt \
+       --extra-index-url https://download.pytorch.org/whl/cpu \
+    && pip uninstall -y poetry poetry-plugin-export \
     && rm requirements.txt
 
 # Copy the rest of the application code to the working directory