This is the actual root cause of "vertical tabs not closeable" —
`render_tab_row` (the rich title+URL rows used in the TABS section)
never rendered a close glyph. Only `render_launcher_row` (favorites
and pinned) had one. So every regular tab in the sidebar was
permanently un-closeable from the sidebar UI; the only path to close
was Cmd+W or the menu.
Restructure render_tab_row from a flex_col (title above URL) to a
flex row: title + URL stack on the left under flex_1+min_w_0, close
glyph on the right with the same group_hover opacity-0 → 1 pattern
the launcher rows use, plus stop_propagation so the row's own
on_click doesn't re-select the just-closed tab.
The two text rows now use `truncate` instead of `overflow_hidden` so
long titles ellipsize cleanly inside the constrained width.
ZacharyZhang-NY
546c3f616d