Review fixes for #462:
- resolveDshHome now treats an empty or whitespace-only $DSH_HOME as
unset, so a blank override never resolves the home to cwd via
resolve(''). Restores the guard telemetry's old resolver carried.
- The default-env telemetry test asserts only that globalConfigDir()
returns an absolute path, so a machine DSH_HOME without a .dsh suffix
cannot break it.