feat(sidecar): supervisor barge endpoints — initiate, mode switch, end

Endpoints:
- GET  /api/supervisor/barge/sip-credentials — fetch SIP number from pool
- POST /api/supervisor/barge — initiate barge via Ozonetel apiId 63
- POST /api/supervisor/barge/mode — update mode (listen/whisper/barge)
- POST /api/supervisor/barge/end — cleanup session + Redis

SupervisorService extended with barge session tracking (in-memory Map).
Mode changes emit SSE events to agent: supervisor-whisper, supervisor-barge,
supervisor-left. Listen mode is silent (no event to agent).

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

src/supervisor/supervisor.service.ts

@@ -34,7 +34,16 @@ export class SupervisorService implements OnModuleInit {
     private readonly activeCalls = new Map<string, ActiveCall>();
     private readonly agentStates = new Map<string, AgentStateEntry>();
     private readonly acwTimers = new Map<string, NodeJS.Timeout>();
-    readonly agentStateSubject = new Subject<{ agentId: string; state: AgentOzonetelState; timestamp: string }>();
+    readonly agentStateSubject = new Subject<{ agentId: string; state: AgentOzonetelState | string; timestamp: string }>();
+
+    // Barge session tracking — key is agentId
+    private readonly bargeSessions = new Map<string, {
+        supervisorId: string;
+        agentId: string;
+        sipNumber: string;
+        mode: 'listen' | 'whisper' | 'barge';
+        startedAt: string;
+    }>();
 
     constructor(
         private platform: PlatformGraphqlService,
@@ -234,4 +243,42 @@ export class SupervisorService implements OnModuleInit {
 
         return { date, agents: summaries, teamTotals };
     }
+
+    // --- Barge session management ---
+
+    getBargeSession(agentId: string) {
+        return this.bargeSessions.get(agentId) ?? null;
+    }
+
+    startBargeSession(session: { supervisorId: string; agentId: string; sipNumber: string; mode: 'listen' | 'whisper' | 'barge'; startedAt: string }) {
+        this.bargeSessions.set(session.agentId, session);
+        this.logger.log(`[BARGE] Started: ${session.supervisorId} → ${session.agentId} (${session.mode})`);
+    }
+
+    updateBargeMode(agentId: string, mode: 'listen' | 'whisper' | 'barge') {
+        const session = this.bargeSessions.get(agentId);
+        if (!session) return;
+
+        const previousMode = session.mode;
+        session.mode = mode;
+
+        // Emit SSE to agent — whisper/barge show indicator, listen is silent
+        if (mode === 'whisper' || mode === 'barge') {
+            this.agentStateSubject.next({ agentId, state: `supervisor-${mode}`, timestamp: new Date().toISOString() });
+        } else if (previousMode !== 'listen') {
+            // Switching back to listen from whisper/barge
+            this.agentStateSubject.next({ agentId, state: 'supervisor-left', timestamp: new Date().toISOString() });
+        }
+
+        this.logger.log(`[BARGE] Mode: ${agentId} → ${mode}`);
+    }
+
+    endBargeSession(agentId: string) {
+        const session = this.bargeSessions.get(agentId);
+        if (!session) return;
+
+        this.bargeSessions.delete(agentId);
+        this.agentStateSubject.next({ agentId, state: 'supervisor-left', timestamp: new Date().toISOString() });
+        this.logger.log(`[BARGE] Ended: ${session.supervisorId} → ${agentId}`);
+    }
 }