reconcileShortLongAliases

Reconcile short/long spellings of the same option in the result map so both keys carry the winning value.

Rule (single source for both docopt overloads): when both spellings are present, a truthy value wins over a falsy one; when both are equally (non)truthy, the long-form value propagates to the short key. With only one spelling present, it is copied to the other.