gui: add session connection status indicator

- Add colored dot to session rows showing tool server RPC status:
  green=connected, yellow=paused+connected, gray=paused, red=broken
- Remove vestigial agent.connected from model (was never displayed)
- Session-level connected status is the correct granularity

gui/main.qml

@@ -198,7 +198,6 @@ ApplicationWindow {
                 agentId: agent.id,
                 level: 1,
                 state: agent.state || "idle",
-                connected: agent.connected,
                 displayName: agent.name,
                 parentExpanded: wasExpanded,
                 parentPaused: isPaused
@@ -311,7 +310,6 @@ ApplicationWindow {
                     // Update agent - use state from session/idx directly
                     var agent = newAgentIds[item.agentId]
                     sessionTreeModel.setProperty(idx, "state", agent.state || "idle")
-                    sessionTreeModel.setProperty(idx, "connected", agent.connected)
                     sessionTreeModel.setProperty(idx, "displayName", agent.name)
                     sessionTreeModel.setProperty(idx, "parentPaused", isPaused)
                 } else {
@@ -346,7 +344,6 @@ ApplicationWindow {
                     agentId: ag.id,
                     level: 1,
                     state: ag.state || "idle",
-                    connected: ag.connected,
                     displayName: ag.name,
                     parentExpanded: wasExpanded,
                     parentPaused: isPaused
@@ -1072,6 +1069,17 @@ ApplicationWindow {
                             }
                         }
 
+                        // Connection status indicator (session rows only)
+                        Rectangle {
+                            Layout.preferredWidth: 8
+                            Layout.preferredHeight: 8
+                            Layout.alignment: Qt.AlignVCenter
+                            Layout.rightMargin: 6
+                            radius: 4
+                            color: connectionColor || "gray"
+                            visible: type === "session"
+                        }
+
                         // Name area
                         Item {
                             Layout.fillWidth: true

gui/ollie9pclient.cpp

@@ -301,7 +301,6 @@ void Ollie9pClient::refreshSessions()
 						av["name"] = agentParts.value(0);
 						av["id"] = agentId;
 						av["state"] = agentParts.value(2);
-						av["connected"] = isConnected;
 						agents.append(av);
 						
 						// Check if this is the active agent