Improve BoardTask to actually report task success/failure
Improve BoardTask to actually report task success/failure

This complements the previous commit. The task bool return value
indicates success or failure.

If the task has failed, BoardTask uses the last report error from
ty_error() on the task thread as the error message.

Koromix/tytools,Koromix/ty,Koromix/ty,Koromix/tytools,Koromix/ty,Koromix/tytools