* feat(tree): replace react-arborist with custom tree implementation
* feat(tree): keyboard arrow navigation between rows
* feat(emoji-picker): focus search input on open
* refactor(emoji): switch to @slidoapp/emoji-mart fork for accessibility
* feat(tree): Home/End and typeahead keyboard navigation
* feat(tree): roving tabindex and * to expand sibling subtrees
* feat(tree): Space activation and ARIA refinements
* fix(tree): move treeitem role to focusable row + aria-current
