Previously the temporary directory was removed via the RETURN trap
but this could be bypassed if the script exited early. Now we
explicitly clean up the directory in all exit paths.
OpenBao now uses raw architecture names (x86_64, aarch64) instead of
Go-style (amd64, arm64) and publishes .tar.gz archives instead of .zip
files. This commit updates the install script to match the new naming
convention and archive format.
```
Update environment variable table formatting for readability
Fix data directory path formatting in README
Add MOTD with OpenBao status and access information
```
