feat(frontend): supervisor presence indicator on agent call card

- useAgentState hook returns { state, supervisorPresence }
- SSE events: supervisor-whisper → "Supervisor coaching" (blue badge)
  supervisor-barge → "Supervisor on call" (brand badge)
  supervisor-left → badge disappears
- Listen mode is silent — no badge shown
- Updated call sites: sidebar.tsx, agent-status-toggle.tsx destructure

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/layout/sidebar.tsx

@@ -132,7 +132,7 @@ export const Sidebar = ({ activeUrl = "/" }: SidebarProps) => {
     const [collapsed, setCollapsed] = useAtom(sidebarCollapsedAtom);
     const agentConfig = typeof window !== 'undefined' ? localStorage.getItem('helix_agent_config') : null;
     const agentId = agentConfig ? (() => { try { return JSON.parse(agentConfig).ozonetelAgentId; } catch { return null; } })() : null;
-    const ozonetelState = useAgentState(agentId);
+    const { state: ozonetelState } = useAgentState(agentId);
     const avatarStatus: 'online' | 'offline' = ozonetelState === 'ready' ? 'online' : 'offline';
 
     const width = collapsed ? COLLAPSED_WIDTH : EXPANDED_WIDTH;