feat(ui): add operator UI server, stores, and insights

docs/runtime-events.md

@@ -28,6 +28,13 @@ Core emitted event types:
 - `session.failed`
 - `security.<security_audit_event_type>` (mirrored from security audit engine)
 
+`node.attempt.completed` metadata includes orchestration-debug fields used by the operator UI:
+
+- `status`, optional `failureKind`, optional `failureCode`
+- `executionContext` (`phase`, `modelConstraint`, `allowedTools`, security constraints)
+- `topologyKind`, `retrySpawned`, optional `fromNodeId`
+- optional `subtasks`, `securityViolation`
+
 ## Sinks
 
 - File sink (`AGENT_RUNTIME_EVENT_LOG_PATH`)