VERIFY-THEN-FIX: the plan-authoring discovery is CONFIRMED. No code anywhere in
src/ registered IOperationTrackingStore in DI, yet AkkaHostedService and
AuditLog SCE both comment that AddSiteRuntime provides it. Every consumer
resolved it via GetService (null-tolerant) and silently ran degraded:
cached-drain scheduler never armed, PullSiteCalls reconciliation seam never
wired, Tracking.Status degraded to audit-only. This is a FUNCTIONAL FIX riding
the hygiene plan: AddSiteRuntime now registers the store (site-only), so
site-local cached-call tracking runs in its intended mode. OperationTrackingOptions
is now bound + eagerly validated in the Host site-options block.