feat(sync): seamless conversation sync, git-like version control, and offline remote notification

lib/store.mjs

@@ -157,4 +157,35 @@ export class Store {
     this.data.master = m
     this.save()
   }
+
+  // ---- session version control & offline notification queue ----------------
+  sessionLineage() { return (this.data.sessionLineage ||= {}) }
+
+  recordLineage(sessionId, info) {
+    const table = this.sessionLineage()
+    table[sessionId] = { ...(table[sessionId] || {}), ...info, updatedAt: Date.now() }
+    this.save()
+    return table[sessionId]
+  }
+
+  pendingMoves() { return (this.data.pendingMoves ||= {}) }
+
+  queueMoveNotice(notice) {
+    const key = `${notice.fromDevice}:${notice.sessionId}`
+    this.pendingMoves()[key] = { ...notice, queuedAt: Date.now() }
+    this.save()
+  }
+
+  popPendingMovesForDevice(deviceId) {
+    const moves = this.pendingMoves()
+    const matching = []
+    for (const [k, v] of Object.entries(moves)) {
+      if (v.fromDevice === deviceId) {
+        matching.push(v)
+        delete moves[k]
+      }
+    }
+    if (matching.length > 0) this.save()
+    return matching
+  }
 }