Show currently-computed path on saveinput if valid

re-use space used by the validation error label Show fully-resolved path, but try to show it relative to `~` if that works. e.g.: - user types `./foo`, show `~/projects/data_project/foo` if cwd is `~/projects/data_project` - user types `./foo`, show `/tmp/abc123/foo` if cwd is `/tmp/abc123` see https://github.com/tconbeer/harlequin/discussions/511