feat: MVP-5 Sprint 3 - Sidebar, Work Mode, and Drafts

- Enhance note-connections with collapsible sections and recent versions
- Add work mode toggle in header for focused work
- Add draft autosave with 7-day TTL and recovery banner
- Save drafts on changes for new notes

src/components/header.tsx

@@ -6,6 +6,7 @@ import { usePathname } from 'next/navigation'
 import { Button } from '@/components/ui/button'
 import { Plus, FileText, Settings, Menu, X } from 'lucide-react'
 import { QuickAdd } from '@/components/quick-add'
+import { WorkModeToggle } from '@/components/work-mode-toggle'
 
 export function Header() {
   const pathname = usePathname()
@@ -43,6 +44,7 @@ export function Header() {
           </nav>
           <div className="flex items-center gap-2">
             <QuickAdd />
+            <WorkModeToggle />
             <Link href="/new">
               <Button size="sm" className="gap-1.5">
                 <Plus className="h-4 w-4" />
@@ -59,6 +61,7 @@ export function Header() {
           </Link>
           <div className="flex items-center gap-2">
             <QuickAdd />
+            <WorkModeToggle />
             <Button
               variant="ghost"
               size="sm"