fix stuck 'Agent is thinking' + flip activity to old-to-new

- AgentIndicator now shows only during stream or when running tools exist
  (not on session status=executing which never cleared)
- Activity timeline: oldest-first ordering (reads top-to-bottom naturally)
- Removed unused liveStatus derivation and currentTask import from Chat
- Plan: Phase A+B+C for activity gaps + plan-approve-once policy

web/src/lib/stores/activity.ts

@@ -127,8 +127,8 @@ export const activityLog = derived([messages, planSteps, currentTask], ([$msgs,
     })
   }
 
-  // Sort newest first
-  entries.sort((a, b) => b.timestamp - a.timestamp)
+  // Sort oldest first
+  entries.sort((a, b) => a.timestamp - b.timestamp)
 
   return entries
 })