Browser-Tab-Manager/Study/message flow from extension.md

Message Flow FROM Extension:

Browser Extension
      ↓ postMessage
window.onMessage
      ↓ (ExtensionService listening)
setupListener() receives message
      ↓ filter by source
_handleExtensionMessage()
      ↓ check action type
Call appropriate callback
      ↓
onTabsUpdate() / onTrackingStart() / onTrackingStop()
      ↓
TabManagerHome updates UI
      ↓
User sees changes!

Message Flow TO Extension:

User clicks "Track Tabs"
      ↓
TabManagerHome calls startTracking()
      ↓
ExtensionService.startTracking()
      ↓
sendMessage({'action': 'startTracking'})
      ↓
window.postMessage
      ↓
Extension receives message
      ↓
Extension starts tracking
      ↓
Extension sends back confirmation