dockerimg: switch to a debian base image

Developing on a musl-based alpine image seems to suck.
A lot of python stuff doesn't work.
Even when told it's alpine, LLMs still want to apt-get install things.

Along with switching to debian, simplify everything.
We *always* use debian bookwork now. If there are python
things, the LLM needs to install them on top of the model.
This will make fallback mode easier: if a build fails, then we
drop ExtraCmds and try again. (Future work.)

While here: avoid using docker buildx in tests because
it seems to vary a lot version-to-version.
diff --git a/dockerimg/testdata/testcreatedockerfile_python_misery.dockerfile b/dockerimg/testdata/testcreatedockerfile_python_misery.dockerfile
index 3eba1c6..d61eed3 100644
--- a/dockerimg/testdata/testcreatedockerfile_python_misery.dockerfile
+++ b/dockerimg/testdata/testcreatedockerfile_python_misery.dockerfile
@@ -1,16 +1,4 @@
-FROM ghcr.io/astral-sh/uv:python3.11-alpine
-
-RUN apk add bash git make jq sqlite gcc musl-dev linux-headers npm nodejs go github-cli ripgrep fzf python3 curl vim grep
-
-ENV GOTOOLCHAIN=auto
-ENV GOPATH=/go
-ENV PATH="$GOPATH/bin:$PATH"
-
-RUN go install golang.org/x/tools/cmd/goimports@latest
-RUN go install golang.org/x/tools/gopls@latest
-RUN go install mvdan.cc/gofumpt@latest
-
-RUN mkdir -p /root/.cache/sketch/webui
+FROM ghcr.io/boldsoftware/sketch:8ad6c62da599d2e478ef79d6ef563630
 
 ARG GIT_USER_EMAIL
 ARG GIT_USER_NAME
@@ -18,20 +6,16 @@
 RUN git config --global user.email "$GIT_USER_EMAIL" && \
     git config --global user.name "$GIT_USER_NAME"
 
-LABEL sketch_context="7010851bfbb48df3a934ebc3eeff896d406d5f37c6a04d82a5ccdf403374d055"
 COPY . /app
 
 WORKDIR /app
 RUN if [ -f go.mod ]; then go mod download; fi
 
-RUN apk add go || true
+# Install Python 3.11 and ensure it's the default python3
+RUN apt-get update && apt-get install -y --no-install-recommends python3.11 python3.11-venv python3-pip || true
+RUN update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.11 1
 
-# Install DVC as mentioned in the README
-RUN uv pip install --system dvc || true
-
-# Make sure Go tools are still installed in this Python-based image
-RUN go install golang.org/x/tools/cmd/goimports@latest || true
-RUN go install golang.org/x/tools/gopls@latest || true
-RUN go install mvdan.cc/gofumpt@latest || true
+# Install DVC tool
+RUN pip3 install dvc || true
 
 CMD ["/bin/sketch"]