fix(messaging): a sent message no longer shows "Seen" instantly

Two independent defects; either alone caused it, in DMs, groups and channels.

1. useMessages reported a read of the newest NON-PENDING message regardless of
   author. Sending therefore made the client immediately mark its own message
   read, the server echoed a receipt for it, and the sender's bubble showed
   "Seen" before anyone had opened the thread. You do not read your own message:
   lastReadableId now skips your own.

2. The guard meant to catch exactly this — `e.actorId !== currentActorId` — could
   never fire: the receipt carries the reader's IIOS actor UUID while clients hold
   a userId, so the comparison was always true and every receipt, including your
   own, counted as the other side. The gateway now also emits userId on READ and
   DELIVERED receipts (matching what `annotation` already did), and ReceiptEvent
   carries it as optional so older servers still typecheck.

MockAdapter.markRead was a no-op, so it could not exercise any of this; it now
echoes a receipt like a real server. Regression test verified to fail without
the fix. SDK 0.1.14; suite 17 files / 101 tests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/iios-messaging-ui/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@insignia/iios-messaging-ui",
-  "version": "0.1.13",
+  "version": "0.1.14",
   "type": "module",
   "main": "dist/index.js",
   "module": "dist/index.js",