refactor(auditlog): consolidate SiteCall DTO mapper into Communication

Extract the verbatim-duplicated SiteCallOperationalDto -> SiteCall mapper
into a single public SiteCallDtoMapper static class in
ScadaLink.Communication.Grpc, mirroring AuditEventDtoMapper. Replaces three
identical private copies (SiteStreamGrpcServer.MapSiteCallFromDto,
ClusterClientSiteAuditClient.MapSiteCall, and the test-infra
DirectActorSiteStreamAuditClient.MapSiteCallFromDto), removes the now-stale
doc comment that justified the duplication, and drops the using directives
that became unused. Adds SiteCallDtoMapperTests for field-by-field coverage.

Only the FromDto direction is provided: nothing maps SiteCall back onto the
wire, so a ToDto would be dead code.

src/ScadaLink.AuditLog/Site/Telemetry/ClusterClientSiteAuditClient.cs

@@ -1,7 +1,6 @@
 using Akka.Actor;
 using ScadaLink.Commons.Entities.Audit;
 using ScadaLink.Commons.Messages.Audit;
-using ScadaLink.Commons.Types;
 using ScadaLink.Communication.Grpc;
 
 namespace ScadaLink.AuditLog.Site.Telemetry;
@@ -92,7 +91,7 @@ public sealed class ClusterClientSiteAuditClient : ISiteStreamAuditClient
         foreach (var packet in batch.Packets)
         {
             var audit = AuditEventDtoMapper.FromDto(packet.AuditEvent);
-            var siteCall = MapSiteCall(packet.Operational);
+            var siteCall = SiteCallDtoMapper.FromDto(packet.Operational);
             entries.Add(new CachedTelemetryEntry(audit, siteCall));
         }
 
@@ -115,31 +114,4 @@ public sealed class ClusterClientSiteAuditClient : ISiteStreamAuditClient
         }
         return ack;
     }
-
-    /// <summary>
-    /// Translates a <see cref="SiteCallOperationalDto"/> into the
-    /// <see cref="SiteCall"/> persistence entity. Mirrors
-    /// <c>SiteStreamGrpcServer.MapSiteCallFromDto</c> — there is no shared
-    /// mapper because that lives in <c>ScadaLink.Communication</c> as a private
-    /// helper. <see cref="SiteCall.IngestedAtUtc"/> is a placeholder; the
-    /// central <c>AuditLogIngestActor</c> overwrites it inside the dual-write
-    /// transaction so the AuditLog and SiteCalls rows share one instant.
-    /// </summary>
-    private static SiteCall MapSiteCall(SiteCallOperationalDto dto) => new()
-    {
-        TrackedOperationId = TrackedOperationId.Parse(dto.TrackedOperationId),
-        Channel = dto.Channel,
-        Target = dto.Target,
-        SourceSite = dto.SourceSite,
-        Status = dto.Status,
-        RetryCount = dto.RetryCount,
-        LastError = string.IsNullOrEmpty(dto.LastError) ? null : dto.LastError,
-        HttpStatus = dto.HttpStatus,
-        CreatedAtUtc = DateTime.SpecifyKind(dto.CreatedAtUtc.ToDateTime(), DateTimeKind.Utc),
-        UpdatedAtUtc = DateTime.SpecifyKind(dto.UpdatedAtUtc.ToDateTime(), DateTimeKind.Utc),
-        TerminalAtUtc = dto.TerminalAtUtc is null
-            ? null
-            : DateTime.SpecifyKind(dto.TerminalAtUtc.ToDateTime(), DateTimeKind.Utc),
-        IngestedAtUtc = DateTime.UtcNow, // overwritten by AuditLogIngestActor
-    };
 }

src/ScadaLink.Communication/Grpc/SiteCallDtoMapper.cs

@@ -0,0 +1,70 @@
+using ScadaLink.Commons.Entities.Audit;
+using ScadaLink.Commons.Types;
+
+namespace ScadaLink.Communication.Grpc;
+
+/// <summary>
+/// Canonical bridge for Site Call Audit (#22) operational rows between the
+/// wire-format <see cref="SiteCallOperationalDto"/> exchanged on the
+/// <c>CachedCallTelemetry</c> packet and the in-process <see cref="SiteCall"/>
+/// persistence entity central writes into the <c>SiteCalls</c> table.
+/// </summary>
+/// <remarks>
+/// <para>
+/// This mapper lives in <c>ScadaLink.Communication</c> (which owns the generated
+/// <see cref="SiteCallOperationalDto"/> and references <c>Commons</c> for
+/// <see cref="SiteCall"/>) so both <c>SiteStreamGrpcServer</c> and
+/// <c>ScadaLink.AuditLog</c> can share one implementation without the
+/// project-reference cycle that would result from hosting it in
+/// <c>ScadaLink.AuditLog</c> (AuditLog → Communication, never the reverse).
+/// Mirrors the sibling <see cref="AuditEventDtoMapper"/>.
+/// </para>
+/// <para>
+/// Only the DTO→entity direction is provided: nothing in the system maps a
+/// <see cref="SiteCall"/> back onto the wire (sites emit the operational state
+/// from <c>SiteCallOperational</c>, never from the central <see cref="SiteCall"/>
+/// entity), so an entity→DTO method would be dead code.
+/// </para>
+/// <para>
+/// String nullability convention: proto3 scalar strings cannot be absent, so the
+/// optional <see cref="SiteCall.LastError"/> rehydrates from an empty string back
+/// to null. The optional <c>HttpStatus</c> and <c>TerminalAtUtc</c> use proto
+/// wrappers so they preserve true null semantics.
+/// </para>
+/// </remarks>
+public static class SiteCallDtoMapper
+{
+    /// <summary>
+    /// Reconstructs a <see cref="SiteCall"/> persistence entity from its
+    /// wire-format DTO. An empty <c>LastError</c> rehydrates as null; absent
+    /// <c>HttpStatus</c>/<c>TerminalAtUtc</c> wrappers stay null.
+    /// </summary>
+    /// <remarks>
+    /// <see cref="SiteCall.IngestedAtUtc"/> is stamped here as a placeholder
+    /// (<see cref="DateTime.UtcNow"/>); the central ingest actor overwrites it
+    /// inside the dual-write transaction so the AuditLog and SiteCalls rows
+    /// share one instant. The value sent on the wire is informational only.
+    /// </remarks>
+    public static SiteCall FromDto(SiteCallOperationalDto dto)
+    {
+        ArgumentNullException.ThrowIfNull(dto);
+
+        return new SiteCall
+        {
+            TrackedOperationId = TrackedOperationId.Parse(dto.TrackedOperationId),
+            Channel = dto.Channel,
+            Target = dto.Target,
+            SourceSite = dto.SourceSite,
+            Status = dto.Status,
+            RetryCount = dto.RetryCount,
+            LastError = string.IsNullOrEmpty(dto.LastError) ? null : dto.LastError,
+            HttpStatus = dto.HttpStatus,
+            CreatedAtUtc = DateTime.SpecifyKind(dto.CreatedAtUtc.ToDateTime(), DateTimeKind.Utc),
+            UpdatedAtUtc = DateTime.SpecifyKind(dto.UpdatedAtUtc.ToDateTime(), DateTimeKind.Utc),
+            TerminalAtUtc = dto.TerminalAtUtc is null
+                ? null
+                : DateTime.SpecifyKind(dto.TerminalAtUtc.ToDateTime(), DateTimeKind.Utc),
+            IngestedAtUtc = DateTime.UtcNow, // overwritten by AuditLogIngestActor
+        };
+    }
+}

src/ScadaLink.Communication/Grpc/SiteStreamGrpcServer.cs

@@ -7,7 +7,6 @@ using Microsoft.Extensions.Options;
 using ScadaLink.Commons.Entities.Audit;
 using ScadaLink.Commons.Interfaces.Services;
 using ScadaLink.Commons.Messages.Audit;
-using ScadaLink.Commons.Types;
 using GrpcStatus = Grpc.Core.Status;
 
 namespace ScadaLink.Communication.Grpc;
@@ -326,7 +325,7 @@ public class SiteStreamGrpcServer : SiteStreamService.SiteStreamServiceBase
         foreach (var packet in request.Packets)
         {
             var auditEvent = AuditEventDtoMapper.FromDto(packet.AuditEvent);
-            var siteCall = MapSiteCallFromDto(packet.Operational);
+            var siteCall = SiteCallDtoMapper.FromDto(packet.Operational);
             entries.Add(new CachedTelemetryEntry(auditEvent, siteCall));
         }
 
@@ -451,31 +450,6 @@ public class SiteStreamGrpcServer : SiteStreamService.SiteStreamServiceBase
         return response;
     }
 
-    /// <summary>
-    /// Translates a <see cref="SiteCallOperationalDto"/> into the persistence
-    /// entity. <see cref="SiteCall.IngestedAtUtc"/> is stamped here as a
-    /// placeholder; the central ingest actor overwrites it inside the
-    /// dual-write transaction so the AuditLog and SiteCalls rows share one
-    /// instant.
-    /// </summary>
-    private static SiteCall MapSiteCallFromDto(SiteCallOperationalDto dto) => new()
-    {
-        TrackedOperationId = TrackedOperationId.Parse(dto.TrackedOperationId),
-        Channel = dto.Channel,
-        Target = dto.Target,
-        SourceSite = dto.SourceSite,
-        Status = dto.Status,
-        RetryCount = dto.RetryCount,
-        LastError = string.IsNullOrEmpty(dto.LastError) ? null : dto.LastError,
-        HttpStatus = dto.HttpStatus,
-        CreatedAtUtc = DateTime.SpecifyKind(dto.CreatedAtUtc.ToDateTime(), DateTimeKind.Utc),
-        UpdatedAtUtc = DateTime.SpecifyKind(dto.UpdatedAtUtc.ToDateTime(), DateTimeKind.Utc),
-        TerminalAtUtc = dto.TerminalAtUtc is null
-            ? null
-            : DateTime.SpecifyKind(dto.TerminalAtUtc.ToDateTime(), DateTimeKind.Utc),
-        IngestedAtUtc = DateTime.UtcNow, // overwritten by AuditLogIngestActor
-    };
-
     /// <summary>
     /// Tracks a single active stream so cleanup only removes its own entry.
     /// </summary>