Format list as an aligned table

The name is what the eye looks for, but it came last, behind a ragged
date column, so nothing lined up. Worse, colorRepoLine rebuilt the line
with strings.Fields and single spaces, which destroyed the alignment ls
had produced -- the output was aligned only when colour was off.

The listing line is now parsed properly instead of being split at the
size field: name, date and size come out as fields, the date is re-padded
to a fixed twelve columns so "Sep 28  2016" and "Jan  3 14:32" agree, and
the name leads in a column sized to the longest entry. Colour decorates
that layout without changing it, which a test now checks by stripping the
escapes and comparing. `list -a` shows archive sizes, which were parsed
and thrown away before.

An empty result says so instead of printing nothing, which was
indistinguishable from a failure, and the count line matches the rest of
mgsh. The pattern now filters on the repository name rather than the
whole listing line: matching the owner or the date was never intended and
`list 2016` quietly did it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

version.txt

@@ -1 +1 @@
-4.0.27
+4.0.29