fix: improve realtime controls layout and add agent status bar

- Change realtime controls to horizontal layout with fixed height (88px)
- Add orientation prop to VolumeMeter for horizontal/vertical modes
- Create AgentStatusBar component showing mode badge and agent status
- Add agent persistence system for managing agent state across restarts
- Fix bottom sheet dismiss handling to clear state properly
- Remove debug timer from realtime controls

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

packages/app/src/components/global-footer.tsx

@@ -72,6 +72,9 @@ const styles = StyleSheet.create((theme) => ({
     borderTopWidth: theme.borderWidth[1],
     borderTopColor: theme.colors.border,
   },
+  realtimeContainer: {
+    backgroundColor: theme.colors.background,
+  },
   centeredButtonContainer: {
     padding: theme.spacing[6],
     alignItems: "center",