Adds `debug snapshot --id <int>` to query a running instance's current
attribute values and alarm states without the subscribe/stream overhead
of the debug view. Routes through ManagementActor → CommunicationService
→ site DeploymentManager → InstanceActor using the existing remote query
pattern.
Attributes bound to data connections now initialize with "Uncertain" quality,
distinguishing "never received a value" from "known good" or "connection lost."
Quality is tracked per attribute and included in GetAttributeResponse.
Static attribute SetAttribute calls now persist the override to local SQLite,
surviving restart and failover. On Instance Actor startup, persisted overrides
are loaded on top of the deployed configuration. Redeployment resets all
persisted overrides to the new deployed values.
Cluster Infrastructure: add min-nr-of-members=1 requirement for single-node
operation after failover. Add graceful shutdown / CoordinatedShutdown section
for fast singleton handover during planned maintenance.
Site Runtime: add explicit supervision strategies per actor type (Resume for
coordinators, Stop for short-lived execution actors). Stagger Instance Actor
startup to prevent reconnection storms. Add Tell-vs-Ask usage guidance per
Akka.NET best practices (Tell for hot path, Ask for system boundaries only).
Data Connection Layer: add Connection Actor Model section documenting the
Become/Stash pattern for connection lifecycle state machine.
Health Monitoring: add dead letter count as a monitored metric.
Host: add REQ-HOST-8a for dead letter monitoring (subscribe to EventStream,
log at Warning level, report as health metric).
Scripts now choose per invocation whether an external system call is synchronous
(all failures return to script) or cached (transient failures go to store-and-forward).
Mirrors the existing Database.Connection/CachedWrite pattern. Updated ESG, Site
Runtime script API, high-level requirements, and design doc.
Add connection lifecycle (fixed-interval auto-reconnect, immediate bad quality on
disconnect, transparent re-subscribe), synchronous write failure errors to scripts,
periodic tag path resolution retry, and enhanced health reporting with tag resolution
counts. Update cross-references in Health Monitoring and Site Runtime.
