Improvements to reference installation shell scripts

just keeping track of some small improvements we can make to installation shell scripts!

- `set -ex` at the top!
- add `apt update`
- see if there's a way to automatically 'Y' to the package installs
- copy the Go binary and client binary into the system binary path, `/usr/local/bin`
- more robust `if [ -f "$FILE" ]` checks before deleting directories - assume this will be rerun
- run through shell check
- use `pushd` and `popd` instead of `cd`
- set GO_VERSION as a constant and template it into the Go install section
- set optional constant for persistent peers

Inspect the reference installation shell scripts and compare them with each requested improvement, including shellcheck validation. Confirm the scripts handle reruns, package installation, binary placement, Go version configuration, directory navigation, and optional persistent peers as described; completion should cover the applicable checklist items.

Written by the indexing model from the issue text.