docs: S2 docs layout + general improvements (#9159)
* close SearchMenu on client navigation
* add footer
* made Nav and ToC widths static
* fix min-height issue on mobile
* show Toast if route can't load
* add toast for clipboard copy failures
* fix React insertion effect
* improve markdown menu
* add skeleton loading for client routing
* copy update
* remote extra startTransitions and use use hook
* improve skeleton loading and optimistic render link selection + ToC
* add delay to showing skeleton
* fix getPageInfo logic
* try fixing getPageInfo again
* try fixing normalizePathname on build
* add prefetch onPressStart
* revert optimistic UI and show error toast if fetch fails
* fix skeleton title
* don't clear targetPathname until new navigation
* move prefetch to a global pointerover listener
* close search menu when navigation starts
* show skeleton loading immediately when navigation starts
* re-use tag group in SearchMenu and MobileSearchMenu
* fix and extract out search logic
* remove blog and releases index pages from search
* reduce size of icons in dnd blog post example
* fix Forms password example
* centralize search logic
* add escapeKeyBehavior="none" to tag groups
* fix toc scroll mask
* simplify pathname logic
* remove promises from prefetch cache once resolved
* use useOptimistic
* use fetchRSC promise as loading source
* avoid navigation race conditions
* prefetch on focus (same as pointerover)
* function for checking if client link
* fix search results sorting for All tag
* add message to currentAbortController.abort
* lint
