repo mirror list: rename REPO column and --repo flag to NAME

Under the entire repo mirror group, the column header REPO and the --repo filter stutter against the group noun. Rename the column to NAME (owner/repo) (inline hint spells out the composite value) and the filter to --name. --name still matches the whole owner/repo string.

parseSortColumn now accepts a column header with its trailing parenthetical hint stripped, so the friendly --sort name resolves the NAME column alongside the full --sort "name (owner/repo)".

--json output is unchanged: it serializes the raw coreapi model, not the column headers, so the wire field stays "repo" and scripts don't break.