gui: fix chat not reloading on session switch

The C++ connection mapping activeSessionIdChanged to chatModel->reset()
raced against the QML onActiveSessionIdChanged handler which does the
actual reload (reset → readLogForSession → appendData → trimFront).
When the C++ slot fired after the QML handler, it cleared the freshly
loaded chat data.

Remove the redundant C++ connection — the QML handler owns the full
reset+reload sequence and sequences the 9P log read correctly.

gui/main.cpp

@@ -28,9 +28,11 @@ int main(int argc, char *argv[])
     auto *chatModel = new ChatBlockModel(&app);
     auto *theme = new ThemeManager(&app);
 
-    // Route chat stream to the block model
+    // Route chat stream to the block model.
+    // Reset + reload is handled in QML's onActiveSessionIdChanged so the
+    // readLogForSession 9P call is sequenced correctly; the C++ slot would
+    // fire before the QML handler and race against the log read.
     QObject::connect(ollie, &Ollie9pClient::chatReceived, chatModel, &ChatBlockModel::appendData);
-    QObject::connect(ollie, &Ollie9pClient::activeSessionIdChanged, chatModel, &ChatBlockModel::reset);
 
     engine.rootContext()->setContextProperty("ollie", ollie);
     engine.rootContext()->setContextProperty("chatModel", chatModel);