feat(03-02): SSE connection manager, SSE endpoint, and command controller

- SseConnectionManager with per-agent SseEmitter, ping keepalive, event delivery
- AgentSseController GET /{id}/events SSE endpoint with Last-Event-ID support
- AgentCommandController with single/group/broadcast command targeting + ack
- WebConfig excludes SSE events path from protocol version interceptor

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cameleer3-server-app/src/main/java/com/cameleer3/server/app/config/WebConfig.java

@@ -28,7 +28,8 @@ public class WebConfig implements WebMvcConfigurer {
                         "/api/v1/health",
                         "/api/v1/api-docs/**",
                         "/api/v1/swagger-ui/**",
-                        "/api/v1/swagger-ui.html"
+                        "/api/v1/swagger-ui.html",
+                        "/api/v1/agents/*/events"
                 );
     }
 }