gui: add agent state indicator dot to session tree

Small colored dot to the right of agent name shows execution state:
- Green: idle
- Blue: thinking
- Orange: calling tool
- Gray: paused

Updates reactively via agentStateChanged event signal.

kde/gui/SessionTree.qml

@@ -291,6 +291,36 @@ Item {
                                 visible: modelIndex !== renamingIndex
                             }
                         }
+
+                        // Agent state indicator (agent rows only)
+                        Rectangle {
+                            id: stateIndicator
+                            Layout.preferredWidth: 8
+                            Layout.preferredHeight: 8
+                            Layout.alignment: Qt.AlignVCenter
+                            Layout.leftMargin: 4
+                            radius: 4
+                            visible: type === "agent"
+                            color: {
+                                var state = ollie.agentState(parentId || "", agentId || "")
+                                if (state.startsWith("calling")) return "#f0a030"  // orange - calling tool
+                                if (state === "thinking") return "#3080f0"         // blue - thinking
+                                if (state === "paused") return "#808080"           // gray - paused
+                                return "#40c040"                                    // green - idle
+                            }
+
+                            Connections {
+                                target: ollie
+                                function onAgentStateChanged(sid, aid, state) {
+                                    if (type === "agent" && sid === parentId && aid === agentId) {
+                                        if (state.startsWith("calling")) stateIndicator.color = "#f0a030"
+                                        else if (state === "thinking") stateIndicator.color = "#3080f0"
+                                        else if (state === "paused") stateIndicator.color = "#808080"
+                                        else stateIndicator.color = "#40c040"
+                                    }
+                                }
+                            }
+                        }
                     }
 
                     highlighted: (type === "agent" && agentId === ollie.activeAgentId && parentId === ollie.activeSessionId)