* feat: darken title bar headers for visual separation from content Add --bg-titlebar (#EDECE9) CSS variable and apply it to all four header bars (TabBar, SidebarTitleBar, NoteList header, Inspector header) so the top drag region is subtly darker than the app content. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com> * docs: add design file for titlebar-darker task Single frame showing the three-tier color hierarchy: title bar (#EDECE9) → sidebar (#F7F6F3) → content (#FFFFFF). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com> --------- Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>