fix: refresh lastUpdate on all message.part.updated events, not just tool events

Reasoning/thinking models (Oracle, Claude Opus) were being killed by the
stale timeout because lastUpdate was only refreshed on tool-type events.
During extended thinking, no tool events fire, so after 3 minutes the
task was incorrectly marked as stale and aborted.

Move progress initialization and lastUpdate refresh before the tool-type
conditional so any message.part.updated event (text, thinking, tool)
keeps the task alive.

src/features/background-agent/manager.ts

@@ -662,16 +662,17 @@ export class BackgroundManager {
         this.idleDeferralTimers.delete(task.id)
       }
 
-      if (partInfo?.type === "tool" || partInfo?.tool) {
-        if (!task.progress) {
-          task.progress = {
-            toolCalls: 0,
-            lastUpdate: new Date(),
-          }
+      if (!task.progress) {
+        task.progress = {
+          toolCalls: 0,
+          lastUpdate: new Date(),
         }
+      }
+      task.progress.lastUpdate = new Date()
+
+      if (partInfo?.type === "tool" || partInfo?.tool) {
         task.progress.toolCalls += 1
         task.progress.lastTool = partInfo.tool
-        task.progress.lastUpdate = new Date()
       }
     }