Auto: abcip-2.6 — AOI input/output handling

AOI-aware browse paths: AOI instances now fan out under directional
sub-folders (Inputs/, Outputs/, InOut/) instead of a flat layout. The
sub-folders only appear when at least one member carries a non-Local
AoiQualifier, so plain UDT tags keep the pre-2.6 flat structure.

- Add AoiQualifier enum (Local / Input / Output / InOut) + new property
  on AbCipStructureMember (defaults to Local).
- L5K parser learns ADD_ON_INSTRUCTION_DEFINITION blocks; PARAMETER
  entries' Usage attribute flows through L5kMember.Usage.
- L5X parser captures the Usage attribute on <Parameter> elements.
- L5kIngest maps Usage strings (Input/Output/InOut) to AoiQualifier;
  null + unknown values map to Local.
- AbCipDriver.DiscoverAsync groups directional members under
  Inputs / Outputs / InOut sub-folders when any member is non-Local.
- Tests for L5K AOI block parsing, L5X Usage capture, ingest mapping
  (both formats), and AOI-vs-plain UDT discovery fan-out.

Closes #234

src/ZB.MOM.WW.OtOpcUa.Driver.AbCip/Import/L5kIngest.cs

@@ -59,7 +59,8 @@ public sealed class L5kIngest
                     Name: m.Name,
                     DataType: memberType,
                     Writable: writable,
-                    Description: m.Description));
+                    Description: m.Description,
+                    AoiQualifier: MapAoiUsage(m.Usage)));
             }
             udtIndex[dt.Name] = members;
         }
@@ -119,6 +120,19 @@ public sealed class L5kIngest
     private static bool IsAccessNone(string? externalAccess) =>
         externalAccess is not null && externalAccess.Trim().Equals("None", StringComparison.OrdinalIgnoreCase);
 
+    /// <summary>
+    ///     PR abcip-2.6 — map the AOI <c>Usage</c> attribute string to <see cref="AoiQualifier"/>.
+    ///     Plain UDT members (Usage = null) + unrecognised values map to <see cref="AoiQualifier.Local"/>.
+    /// </summary>
+    private static AoiQualifier MapAoiUsage(string? usage) =>
+        usage?.Trim().ToUpperInvariant() switch
+        {
+            "INPUT" => AoiQualifier.Input,
+            "OUTPUT" => AoiQualifier.Output,
+            "INOUT" => AoiQualifier.InOut,
+            _ => AoiQualifier.Local,
+        };
+
     /// <summary>Map a Logix atomic type name. Returns <c>null</c> for UDT/structure references.</summary>
     private static AbCipDataType? TryMapAtomic(string logixType) =>
         logixType?.Trim().ToUpperInvariant() switch