gui: clicking a session clears explicit agent selection

- Session row click now calls setActiveSessionId(id)
- setActiveSessionId no longer returns early for same-session clicks;
  it always clears m_agentId and stops per-agent streams
- This enforces a clean 'session selected, no agent selected' state

gui/main.qml

@@ -604,6 +604,7 @@ ApplicationWindow {
                             }
                             if (renamingIndex >= 0) return
                             if (type === "session") {
+                                ollie.setActiveSessionId(id)
                                 toggleExpand(parent.modelIndex)
                             } else if (type === "agent") {
                                 activateAgent(parentId, agentId)

gui/ollie9pclient.cpp

@@ -49,8 +49,9 @@ Ollie9pClient::~Ollie9pClient()
 
 void Ollie9pClient::setActiveSessionId(const QString &id)
 {
-	if (m_activeSessionId == id) return;
-
+	// Session selection must be side-effect free for per-agent streams.
+	// Even re-selecting the same session should clear agent selection and stop
+	// statewait/chat so the UI can stay in a pure "session selected" state.
 	stopStreams();
 	m_activeSessionId = id;
 	m_agentId.clear();