dockerimg: add SKETCH=1 to sketch container

Also remove some extra files debian.
diff --git a/dockerimg/testdata/testcreatedockerfile_empty_repo.dockerfile b/dockerimg/testdata/testcreatedockerfile_empty_repo.dockerfile
index 94010f1..0ae81e9 100644
--- a/dockerimg/testdata/testcreatedockerfile_empty_repo.dockerfile
+++ b/dockerimg/testdata/testcreatedockerfile_empty_repo.dockerfile
@@ -1,4 +1,4 @@
-FROM ghcr.io/boldsoftware/sketch:8ad6c62da599d2e478ef79d6ef563630
+FROM ghcr.io/boldsoftware/sketch:86ef7a672f85139e73f38d4cdf78d95f
 
 ARG GIT_USER_EMAIL
 ARG GIT_USER_NAME
@@ -6,19 +6,23 @@
 RUN git config --global user.email "$GIT_USER_EMAIL" && \
     git config --global user.name "$GIT_USER_NAME"
 
-LABEL sketch_context="8680db4c498365658a6e773fde0d43f642ae6744f41a14ad6d01e9eae7064f65"
+LABEL sketch_context="5820b50cae54d2fbdd28081f960dcfac4367f8d805030ecd612a13ebeef13bb1"
 COPY . /app
 
 WORKDIR /app
 RUN if [ -f go.mod ]; then go mod download; fi
 
-# Install any Python dependencies but continue on error
-RUN if [ -f requirements.txt ]; then pip3 install -r requirements.txt || true; fi
+RUN --mount=type=cache,target=/var/cache/apt \
+    set -eux; \
+    apt-get update && \
+    apt-get install -y --no-install-recommends python3-pip python3-venv || true
 
-# Setup Go environment properly
-RUN if [ -f go.sum ]; then go mod tidy || true; fi
+# Set up Python environment, allowing failures to not stop the build
+RUN python3 -m pip install --upgrade pip || true
 
-# Make sure build scripts are executable
-RUN find . -name "*.sh" -exec chmod +x {} \; || true
+# Install any Go tools specific to this project if needed
+RUN --mount=type=cache,target=/go/pkg/mod \
+    --mount=type=cache,target=/root/.cache/go-build \
+    go install github.com/golangci/golangci-lint/cmd/golangci-lint@latest || true
 
 CMD ["/bin/sketch"]