feat: deliver leader summaries by webhook

.env.example

@@ -25,6 +25,10 @@ AGENTBUS_CLIENT_TYPE=bot
 AGENTBUS_WS_RECONNECT_DELAY=5s
 AGENTBUS_TASK_TIMEOUT_MS=300000
 AGENTBUS_LOG_PAYLOADS=false
+# Optional organization-wide team-lead summary delivery. Configure both values
+# to enable; keep secrets in the protected runtime environment only.
+WEBHOOK_SEND_URL=
+WEBHOOK_EXTERNAL_TOKEN=
 # AgentBus/WeChat result attachments require HTTPS OSS URLs; use OSS storage
 # for deployments that send confirmation files to external channels.
 ARTIFACT_STORAGE_BACKEND=database