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.
