Drop the `xfail` test and instead add a new one that ensures the
`tractor._exceptions` fixes enable graceful relay of
remote-but-unregistered error types via the unboxing of just the
`rae.src_type_str/boxed_type_str` content. The test also ensures
a warning is included with remote error content indicating the user
should register their error type for effective cross-actor re-raising.
Deats,
- add `test_unregistered_err_still_relayed`: verify the
`RemoteActorError` IS raised with `.boxed_type`
as `None` but `.src_type_str`, `.boxed_type_str`,
and `.tb_str` all preserved from the IPC msg.
- drop `test_unregistered_boxed_type_resolution_xfail`
since the new above case covers it and we don't need to have
an effectively entirely repeated test just with an inverse assert
as it's last line..
(this patch was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code