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.
Specify HTTP/REST with JSON as the invocation protocol. Add API key and Basic Auth
as outbound authentication modes. Add per-system call timeouts. Classify errors by
HTTP status for store-and-forward decisions (5xx/transient → retry, 4xx → permanent
error to script). Document ADO.NET connection pooling for database connections.
Update Store-and-Forward to clarify transient-only buffering.
