add singularity/apptainer as a possible containerization tech

To make claude usable on HPC and other shared envs where no podman. I am not sure though if always would be possible to build an image, yet to research

Start by locating where this Shell project invokes Podman and review the assumptions that prevent use on HPC or shared environments. Research Singularity/Apptainer image execution and build limitations, then define done as running Claude safely in an environment without Podman.

Written by the indexing model from the issue text.