refactor: no expiring command, and a file's last commit is its hash and age

The status pane already lists what's expiring. The last commit no longer
names who made it or its message.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

internal/provider/repo/details.go

@@ -55,7 +55,7 @@ func (p *Provider) Details(ctx context.Context, c provider.Container) ([]provide
 		}
 		return out, nil
 	}
-	if last, ok := git("log", "-1", "--format=%h · %ar · %an: %s", "--", rel); ok && last != "" {
+	if last, ok := git("log", "-1", "--format=%h · %ar", "--", rel); ok && last != "" {
 		out = append(out, provider.Attr{Label: "last commit", Value: last})
 	}
 	return out, nil