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/lib/drafts.ts

@@ -0,0 +1,36 @@
+const DRAFT_KEY_PREFIX = 'recall_draft_'
+const DRAFT_TTL = 7 * 24 * 60 * 60 * 1000 // 7 days
+
+interface Draft {
+  title: string
+  content: string
+  type: string
+  tags: string[]
+  savedAt: number
+}
+
+export function saveDraft(noteId: string, data: Draft): void {
+  if (typeof window === 'undefined') return
+  localStorage.setItem(DRAFT_KEY_PREFIX + noteId, JSON.stringify({ ...data, savedAt: Date.now() }))
+}
+
+export function loadDraft(noteId: string): Draft | null {
+  if (typeof window === 'undefined') return null
+  const stored = localStorage.getItem(DRAFT_KEY_PREFIX + noteId)
+  if (!stored) return null
+  try {
+    const draft = JSON.parse(stored) as Draft
+    if (Date.now() - draft.savedAt > DRAFT_TTL) {
+      deleteDraft(noteId)
+      return null
+    }
+    return draft
+  } catch {
+    return null
+  }
+}
+
+export function deleteDraft(noteId: string): void {
+  if (typeof window === 'undefined') return
+  localStorage.removeItem(DRAFT_KEY_PREFIX + noteId)
+}