Expose draft updates to iOS bridge

scripts/smoke-ios-ffi-swift.sh

@@ -69,6 +69,15 @@ struct Smoke {
         let voice = try session.downloadVoice(fileId: 200)
         require(voice.path == "/tmp/fake-voice.ogg", "expected downloaded voice path")
 
+        try session.setDraft(chatId: chat.id, text: "Draft from Swift FFI")
+        let draftEvents = session.pollEvents()
+        require(draftEvents.contains {
+            if case let .draftChanged(draft) = $0 {
+                return draft.text == "Draft from Swift FFI"
+            }
+            return false
+        }, "expected draftChanged event")
+
         let sent = try session.sendMessage(chatId: chat.id, text: "Hi from Swift FFI", replyToMessageId: nil)
         require(sent.text == "Hi from Swift FFI", "expected sent message text")