fix(ablegacy): indirect element index up to 999 on PLC-5; clear IndirectLastName on dispose

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy/AbLegacyDriver.cs

@@ -862,6 +862,9 @@ public sealed class AbLegacyDriver : IDriver, IReadable, IWritable, ITagDiscover
     /// <summary>Largest word/element index an indirect source may yield (PCCC element offset is one byte).</summary>
     private const int MaxIndirectElement = AbLegacyArray.MaxElements - 1;
 
+    /// <summary>PLC-5 data files hold up to 1000 words (extended PCCC offset), unlike SLC/MicroLogix (256).</summary>
+    private const int MaxIndirectElementPlc5 = 999;
+
     /// <summary>Largest data-file number an indirect source may yield (PLC-5 allows up to 999).</summary>
     private const int MaxIndirectFile = 999;
 
@@ -877,6 +880,8 @@ public sealed class AbLegacyDriver : IDriver, IReadable, IWritable, ITagDiscover
     {
         var fileNumber = parsed.FileNumber;
         var word = parsed.WordNumber;
+        var maxElement = device.Options.PlcFamily is AbLegacyPlcFamily.Plc5 or AbLegacyPlcFamily.LogixPccc
+            ? MaxIndirectElementPlc5 : MaxIndirectElement;
 
         if (parsed.IndirectFileSource is { } fileSrc)
         {
@@ -890,7 +895,7 @@ public sealed class AbLegacyDriver : IDriver, IReadable, IWritable, ITagDiscover
         {
             var r = await ReadIndexAsync(device, wordSrc, ct).ConfigureAwait(false);
             if (r.Status != 0) return new IndirectResolution(null, r.Status, r.TransportFault);
-            if (r.Value is < 0 or > MaxIndirectElement)
+            if (r.Value < 0 || r.Value > maxElement)
                 return new IndirectResolution(null, AbLegacyStatusMapper.BadOutOfRange, false);
             word = (int)r.Value!;
         }
@@ -1329,6 +1334,7 @@ public sealed class AbLegacyDriver : IDriver, IReadable, IWritable, ITagDiscover
             Runtimes.Clear();
             foreach (var r in ParentRuntimes.Values) r.Dispose();
             ParentRuntimes.Clear();
+            IndirectLastName.Clear();
             // Dispose + clear the per-parent RMW gates and the per-runtime/creation locks so
             // ReinitializeAsync cycles don't orphan their SemaphoreSlim instances (each leaks a
             // wait handle once contended).