A click outside the Kanban sidebar flyout called setOpen(false) even when
the click was on a Link, so the deferred state update landed during the
Link navigation's RSC stream and corrupted Turbopack's flight client
(vercel/next.js#92362).
Skip the close when the click target is inside an <a> and flush the close
synchronously from the Link's own onClick so the state update completes
before navigation, not during RSC processing.
