The existing implementation of the termcurses_deinitterm calls
termcurses_setcolors with some hard-coded values, leading to different
terminal emulators' behavior. Instead, a reset call needs to be made to
the implementation to roll back changes.
A new operation (terminate) has been added to the termcurses_ops interface
to achieve this functionality.
The vt100's terminate implementation ensures that default foreground and
background colors are applied portably across different terminals emulators.
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