a212283104
WP2.6 (arch-review remediation, cross-cutting misc): - SiteExternalSystemRepository: name/ID-indexed ExternalSystemDefinitionCache replaces the fetch-all + reverse-map scan on every by-ID/method lookup; loaded once per redeploy, invalidated by DeploymentManagerActor after HandleDeployArtifacts applies external-system changes. Static JsonSerializerOptions for method-list parsing. - Inbound API: short-TTL ApiMethodCache fronts the per-request ApiMethod repository fetch; invalidated by name via the existing ScriptArtifactChangeSubscriber/ IScriptArtifactChangeBus pipeline, self-healing via TTL for changes the bus doesn't cover (e.g. Management API edits). - StoreAndForward: the cached-call audit-observer queue — the one unbounded channel left in the system — is now bounded (ObserverQueueCapacity, default 10,000) with DropOldest overflow and a dropped-notification counter. - SiteStreamManager: alarm state changes now travel a dedicated publish source/broadcast hub, isolated from the (far higher-volume) attribute path, so an attribute storm can no longer evict a pending alarm transition; the alarm hand-off queue is bounded with a drop counter surfaced on the site health report (SiteStreamAlarmDropCount via the new SiteStreamAlarmDropReporter), and publishing is skipped entirely at zero subscribers on either path. - CLI ManagementHttpClient: explicit 30s HttpClient.Timeout on the shared construction (was the 100s framework default), overridable via SCADABRIDGE_HTTP_TIMEOUT_SECONDS. Deviation: the failback-probe heartbeat item is NOT included — its only viable surface (CentralChannelProvider.cs / heartbeat consumers) lives entirely in the Communication project, explicitly off-limits to this work package this phase. Tests: SiteRuntime.Tests (550), InboundAPI.Tests (278), StoreAndForward.Tests (133), CLI.Tests (390), HealthMonitoring.Tests (97) — all green after full solution build.