fix for #60695 fix Series constructor dropping key levels when keys have varying entry counts
Ensures that the Series constructor preserves all key (index) levels, even when keys have different numbers of entries.
Addresses issue #60695 by maintaining consistency in index handling.

Thanks for the pull request, but it appears to have gone stale. If interested in continuing, please merge in the main branch, address any review comments and/or failing tests, and we can reopen.