feat(dcl+siteruntime): reconfigure a LIVE data connection in place — register row 97

`DataConnectionManagerActor.HandleCreateConnection` is create-only (warns and
returns for a name it already holds), so `EnsureDclConnection`'s documented
"a changed config re-issues the create so the DCL adopts it" was never true on
ANY node: a corrected endpoint/credential/backup/failover-count took effect only
when the connection was next built from scratch (node restart, singleton
failover, remove-then-re-add), while the DM's hash cache recorded it as applied.
Rows 89/90 made that honest with a Warning; this closes it.

New `ReconfigureConnectionCommand` (Commons, same shape as the create):

- `DeploymentManagerActor.EnsureDclConnection` now has three outcomes off its one
  per-name hash slot — unchanged -> nothing at all, new -> create, CHANGED ->
  reconfigure — and logs "Reconfigured DCL connection {Connection}
  (protocol={Protocol}) in place" at Information in place of the old Warning. The
  winner-resolution / arbitration / tombstone logic is untouched; only what
  happens after a change is detected changed.
- `DataConnectionManagerActor` FORWARDS the command to the owning connection
  actor, falling back to a create for a name it does not hold, so the command is
  safe whatever the manager's state.
- `DataConnectionActor` handles it in ALL THREE states and never stashes it — a
  connection pointed at a wrong or dead endpoint lives in Connecting/Reconnecting,
  which is exactly when a correction arrives; stashed it would wait on the broken
  configuration forever. Handling replaces protocol/primary/backup/failover-count,
  re-arms endpoint selection to Primary (the new config's primary is the intent,
  whatever the old config had failed over to), and calls the new shared
  `SwapAdapter` helper — now used by both failover sites too, so the swap exists
  once: unhook + fire-and-forget dispose -> _factory.Create -> rewire -> bump
  _adapterGeneration LAST. `BecomeReconnecting(afterReconfigure: true)` then
  reconnects immediately (StartSingleTimer replaces any armed reconnect, so no
  racing attempts) with the unstable-disconnect accounting and failover check
  suppressed — the link was dropped on purpose, and counting it as an unstable
  cycle could trip a failover onto the NEW backup before the new primary had been
  tried once. ReSubscribeAll/ReSubscribeAllAlarms then re-issue everything from
  the untouched subscription registries. Idempotent: a reconfigure carrying the
  configuration already in force is a no-op.

Stop-and-recreate was rejected as destructive: subscriptions live inside
DataConnectionActor and InstanceActor cancels its subscribe-retry timer on first
success, so a rebuilt actor would have no subscribers and nothing would ever
re-subscribe.

Tests: new DataConnectionReconfigureTests (7; 5 fail / 2 pass against a
behavioural revert). DclConnectionArbitrationTests gains two row-97 tests and its
CDC-arrival test now asserts the second push is a reconfigure; its ping-pong
guard also asserts zero reconfigures, since a flip would now show up there.
SiteRuntime-010 renamed to ..._ReissuesReconfigureCommand. 3 fail against a
reverted EnsureDclConnection. DataConnectionLayer.Tests 327/327,
SiteRuntime.Tests 643/643, solution build 0 warnings.

Docs: Component-DataConnectionLayer.md gains an "In-place reconfiguration"
section under Endpoint Redundancy; Component-SiteRuntime.md, and the
docs/components/ mirrors, updated; the arbitration decision memo gains an
appended §9 postscript resolving its residual 1 (residuals 2 and 3 stay open).

src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Actors/DataConnectionManagerActor.cs

@@ -58,6 +58,7 @@ public class DataConnectionManagerActor : ReceiveActor
         _opcUaGlobalOptions = opcUaGlobalOptions ?? new OpcUaGlobalOptions();
 
         Receive<CreateConnectionCommand>(HandleCreateConnection);
+        Receive<ReconfigureConnectionCommand>(HandleReconfigureConnection);
         Receive<SubscribeTagsRequest>(HandleRoute);
         Receive<UnsubscribeTagsRequest>(HandleRoute);
         Receive<SubscribeAlarmsRequest>(HandleRouteAlarms);
@@ -102,6 +103,40 @@ public class DataConnectionManagerActor : ReceiveActor
             command.ConnectionName, command.ProtocolType);
     }
 
+    /// <summary>
+    /// Applies a new configuration to a LIVE connection actor (deferred register row 97) by
+    /// forwarding the command to it — the actor swaps its adapter in place and re-issues every
+    /// subscription it holds, rather than being stopped and rebuilt (which would silently strand
+    /// every subscriber; see <see cref="ReconfigureConnectionCommand"/>).
+    ///
+    /// <para>
+    /// A name this manager does not hold falls back to <see cref="HandleCreateConnection"/>, so
+    /// the command is safe regardless of manager state: a sender whose view of which connections
+    /// exist is stale (a fresh singleton incarnation, a node that has just taken over) still
+    /// converges on the intended configuration in one message.
+    /// </para>
+    /// </summary>
+    private void HandleReconfigureConnection(ReconfigureConnectionCommand command)
+    {
+        if (_connectionActors.TryGetValue(command.ConnectionName, out var actor))
+        {
+            _log.Info("Reconfiguring DataConnectionActor for {0} in place (protocol={1})",
+                command.ConnectionName, command.ProtocolType);
+            actor.Forward(command);
+            return;
+        }
+
+        _log.Info(
+            "Reconfigure for {0} arrived with no live connection actor — creating it instead",
+            command.ConnectionName);
+        HandleCreateConnection(new CreateConnectionCommand(
+            command.ConnectionName,
+            command.ProtocolType,
+            command.PrimaryConnectionDetails,
+            command.BackupConnectionDetails,
+            command.FailoverRetryCount));
+    }
+
     private void HandleRoute(SubscribeTagsRequest request)
     {
         if (_connectionActors.TryGetValue(request.ConnectionName, out var actor))