* perf(web): eliminate sidebar close lag with many tasks
Closing the app sidebar unmounted the entire task list in the same frame
the width animation started, so close lag scaled with task count.
- Keep the Tasks grow-section mounted but CSS-hidden in rail mode:
collapse is now O(1) and reopening is instant (no remount).
- Memoize onToggleGroup so TaskSwitcher's memo() holds; an inline arrow
re-rendered every task row on each sidebar render.
- Animate only width (transition-[width]) instead of transition-all.
- content-visibility:auto on task blocks skips layout/paint for rows
outside the sidebar scrollport in long lists.
* test(web): add round-trip collapse/expand assertion to sidebar section test
José Almeida
d145874e3b