Return the original rename error unless the move crosses filesystems.
Permission and sharing errors must not start a copy-and-delete operation
that can leave the destination behind or remove source contents.
Preserve the source Windows symlink's file or directory kind rather than
inferring it from a target that may not exist at the destination yet.
Keep relative targets, Developer Mode handling and long-path support.
Cover rename failures, Linux cross-device moves and Windows link kinds,
and run the focused session tests natively in Windows CI.
Zhizhen He
0c6b4c290a