fix: use multiplexed file timestamps in deltas

If the original delta data has timestamps use them, otherwise use the
timestamp of the multiplexed data also in deltas instead of letting the
server fill in the current time.

Fixes #1659.

packages/streams/autodetect.js

@@ -113,6 +113,8 @@ Splitter.prototype._transform = function (msg, encoding, _done) {
       default:
         try {
           const parsed = JSON.parse(msg.data)
+          const timestamp = new Date(Number(msg.timestamp))
+          parsed.updates && parsed.updates.forEach((update) => update.timestamp = timestamp)
           this.push(parsed)
           this.demuxEmitData(parsed)
         } catch (e) {