Make tmux alert parsing and focus more robust

Session names can contain pipes but never colons, so split fields on
colons instead. Remember refreshes that arrive while the indicator is
already polling, and jump to the most recently used tmux client rather
than an arbitrary one.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

shell/plugins/bar/indicators/TmuxAlert.qml

@@ -8,6 +8,7 @@ BarIndicator {
 
   property int waitingCount: 0
   property string tooltip: ""
+  property bool refreshPending: false
 
   active: waitingCount > 0
   activeText: "󰆍"
@@ -16,7 +17,8 @@ BarIndicator {
   inactiveTooltipText: "No terminal is waiting"
 
   function refresh() {
-    if (!statusProc.running) statusProc.running = true
+    if (statusProc.running) refreshPending = true
+    else statusProc.running = true
   }
 
   function update(raw) {
@@ -54,6 +56,11 @@ BarIndicator {
         root.waitingCount = 0
         root.tooltip = ""
       }
+
+      if (root.refreshPending) {
+        root.refreshPending = false
+        root.refresh()
+      }
     }
   }