fix(site-event-logging): resolve SiteEventLogging-006,009,011 — severity index, accurate XML doc, dead-placeholder removal

src/ScadaLink.SiteEventLogging/ISiteEventLogger.cs

@@ -6,14 +6,20 @@ namespace ScadaLink.SiteEventLogging;
 public interface ISiteEventLogger
 {
     /// <summary>
-    /// Record an event asynchronously.
+    /// Record an event asynchronously. The call enqueues the event onto a background
+    /// writer and returns without blocking the caller on disk I/O. The returned
+    /// <see cref="Task"/> completes once the event is durably persisted and faults if
+    /// the write fails, so callers that <c>await</c> it observe success or failure.
     /// </summary>
     /// <param name="eventType">Category: script, alarm, deployment, connection, store_and_forward, instance_lifecycle</param>
     /// <param name="severity">Info, Warning, or Error</param>
     /// <param name="instanceId">Optional instance ID associated with the event</param>
     /// <param name="source">Source identifier, e.g., "ScriptActor:MonitorSpeed"</param>
     /// <param name="message">Human-readable event description</param>
-    /// <param name="details">Optional JSON details (stack traces, compilation errors, etc.)</param>
+    /// <param name="details">
+    /// Optional free-form detail text (stack traces, compilation errors, etc.).
+    /// Stored verbatim — JSON is conventional but not validated or enforced.
+    /// </param>
     Task LogEventAsync(
         string eventType,
         string severity,

src/ScadaLink.SiteEventLogging/ServiceCollectionExtensions.cs

@@ -21,9 +21,9 @@ public static class ServiceCollectionExtensions
         return services;
     }
 
-    public static IServiceCollection AddSiteEventLoggingActors(this IServiceCollection services)
-    {
-        // Placeholder for Akka actor registration (Phase 4+)
-        return services;
-    }
+    // NOTE: EventLogHandlerActor is wired up directly in
+    // ScadaLink.Host/Actors/AkkaHostedService.cs as a cluster singleton, because the
+    // actor must be created inside the ActorSystem with the resolved
+    // IEventLogQueryService. There is intentionally no DI helper for that here — a
+    // former AddSiteEventLoggingActors placeholder was dead code and has been removed.
 }

src/ScadaLink.SiteEventLogging/SiteEventLogger.cs

@@ -123,7 +123,12 @@ public class SiteEventLogger : ISiteEventLogger, IDisposable
             CREATE INDEX IF NOT EXISTS idx_events_timestamp ON site_events(timestamp);
             CREATE INDEX IF NOT EXISTS idx_events_type ON site_events(event_type);
             CREATE INDEX IF NOT EXISTS idx_events_instance ON site_events(instance_id);
+            CREATE INDEX IF NOT EXISTS idx_events_severity ON site_events(severity);
             """;
+        // The query service also supports keyword search via leading-wildcard
+        // LIKE on message/source. A leading-wildcard LIKE cannot use a B-tree
+        // index, so that path intentionally full-scans; severity/event_type/
+        // instance_id/timestamp filters above are all covered.
         cmd.ExecuteNonQuery();
     }