New <toast-host> overlay: components post 'toast' CustomEvents ({message, kind: success|error|info}) and it shows brief, auto-dismissing, bottom-right toasts (errors linger). <repo-menu> (git + coordination actions) and <pr-list> (create/merge) now post friendly success/error toasts instead of alert(); the activity feed still logs everything. Also adds the slice 11 CHANGELOG entry. Verified live: 'Checked for updates' toast shown.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
