Each sidebar launcher row now ships with a 16 px close glyph that fades
in via group_hover. Clicking the glyph selects the row's tab then
closes the active tab — the same flow the split pane close uses.
Matches the design's .ely-nav-item .close opacity-0 → 1 transition
without keeping the X visible at rest.
ZacharyZhang-NY
68e784daf8