Create /workspaces in the devcontainer for the dev user

Folders next to the project, like a clone of another repository, can be
created without root.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.devcontainer/Dockerfile

@@ -27,6 +27,10 @@ RUN groupadd --gid $USER_GID $USERNAME && \
     echo "$USERNAME ALL=(root) NOPASSWD:ALL" > /etc/sudoers.d/$USERNAME && \
     chmod 0440 /etc/sudoers.d/$USERNAME
 
+# Owned by the dev user so folders can be created next to the project. Docker
+# would otherwise create it as root when bind mounting /workspaces/max.
+RUN mkdir /workspaces && chown $USERNAME:$USERNAME /workspaces
+
 # Project venv, owned by the dev user so pip works without sudo
 ENV VIRTUAL_ENV=/opt/venv
 RUN python -m venv $VIRTUAL_ENV && chown -R $USERNAME:$USERNAME $VIRTUAL_ENV