fix(workspace): move lane list to a vertical column beside detail panel

The detail panel (LaneCard/PipelineMap/proof gallery/console) could
grow tall enough to visually crowd out the lane-strip carousel above
it once a run was attached in split view. Move the lane list into its
own scrolling vertical column beside the detail panel instead of
stacking it above, so neither can cover the other; also collapse the
info block by default in 2/4-pane split view (toggle to expand) and
move the pane-count control into the detail header.

client/src/components/lanes/LaneStripCard.tsx

@@ -1,9 +1,9 @@
 /**
- * @file The compact lane tile used in the Workspace carousel. It carries only
- * what you need to pick a lane — which lane, is it alive, what stage, how far —
- * because the full card, its controls and its working-copy facts live in the
- * detail panel below. Keeping the tile small is what lets a dozen lanes stay
- * scannable in one horizontal row.
+ * @file The compact lane tile used in the Workspace's vertical lane list. It
+ * carries only what you need to pick a lane — which lane, is it alive, what
+ * stage, how far — because the full card, its controls and its working-copy
+ * facts live in the detail panel beside it. Keeping the tile small and full
+ * width is what lets many lanes stay scannable in one scrolling column.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
@@ -42,7 +42,7 @@ export default function LaneStripCard({
       aria-pressed={selected}
       onClick={onSelect}
       title={lane.cwd}
-      className={`w-56 shrink-0 snap-start rounded-lg border p-3 text-left shadow-sm transition-colors ${
+      className={`w-full shrink-0 rounded-lg border p-3 text-left shadow-sm transition-colors ${
         selected
           ? "border-accent bg-accent/10"
           : "border-border bg-surface-2 hover:border-border-light hover:bg-surface-3"