nemo-repo-core dropped from 1.0.0 to 0.1.0 while its API is still
unsettled, and requireCore treats the minor as the breaking component in
the 0.x range.
Keeps only the ColumnProvider from the single file extension; the config, git and cache layers come from nemo-repo-core, so the columns share one git query with the other plugins in the family.
The status string moves to the shared RepoInfo.summary and is now plain ASCII: 2 ahead, 1 behind instead of arrow glyphs. Both columns can be turned off in the config.