Move from docker compose run to a Python-managed container lifecycle.
Each project now gets a dedicated container that is started on demand
and stopped when opencode exits, instead of being recreated each time.
Use a shared home directory across projects so configurations presist.
The container are not destroyed, so tools and caches can be installed
specifically for a project by opencode itself once and reused, while
still avoiding long-running containers.
The problem was that we mounted `pwd` as HOME and that meant that
every time git was used it would look into the data and work for a
long time, and it would also commit everything there.
Now we have a central container-home directory in the directory
where we checked out this git repo and it is used by each session
independent of in which project directory we are.
