- Move tab bar into header (centered between title and toolbar) - Make entire header sticky with border-bottom separator - Remove container max-width for full-width layout - Add scroll-spy: tree sidebar tracks visible section on scroll - Remember scroll position per tab when switching - Remove sticky section headers, use scroll-margin-top instead - Update sticky offsets to use --sticky-top CSS variable Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>