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

tests/ZB.MOM.WW.OtOpcUa.Driver.AbCip.Tests/L5kIngestTests.cs

@@ -153,6 +153,81 @@ public sealed class L5kIngestTests
         Should.Throw<InvalidOperationException>(() => new L5kIngest().Ingest(doc));
     }
 
+    [Fact]
+    public void AOI_member_Usage_maps_to_AoiQualifier_through_ingest()
+    {
+        // PR abcip-2.6 — L5K AOI parameters carry a Usage := Input / Output / InOut attribute.
+        // Ingest must map those values onto AbCipStructureMember.AoiQualifier so the discovery
+        // layer can group AOI members under sub-folders. Plain DATATYPE members get Local.
+        const string body = """
+            ADD_ON_INSTRUCTION_DEFINITION ValveAoi
+                PARAMETERS
+                    PARAMETER Cmd : BOOL (Usage := Input) := 0;
+                    PARAMETER Status : DINT (Usage := Output) := 0;
+                    PARAMETER Buffer : DINT (Usage := InOut) := 0;
+                    PARAMETER Local1 : DINT := 0;
+                END_PARAMETERS
+            END_ADD_ON_INSTRUCTION_DEFINITION
+            DATATYPE PlainUdt
+                MEMBER Speed : DINT := 0;
+            END_DATATYPE
+            TAG
+                Valve_001 : ValveAoi;
+                Tank1 : PlainUdt;
+            END_TAG
+            """;
+        var doc = L5kParser.Parse(new StringL5kSource(body));
+
+        var result = new L5kIngest { DefaultDeviceHostAddress = DeviceHost }.Ingest(doc);
+
+        var aoiTag = result.Tags.Single(t => t.Name == "Valve_001");
+        aoiTag.Members.ShouldNotBeNull();
+        aoiTag.Members!.Single(m => m.Name == "Cmd").AoiQualifier.ShouldBe(AoiQualifier.Input);
+        aoiTag.Members.Single(m => m.Name == "Status").AoiQualifier.ShouldBe(AoiQualifier.Output);
+        aoiTag.Members.Single(m => m.Name == "Buffer").AoiQualifier.ShouldBe(AoiQualifier.InOut);
+        aoiTag.Members.Single(m => m.Name == "Local1").AoiQualifier.ShouldBe(AoiQualifier.Local);
+
+        // Plain UDT members default to Local — no Usage attribute to map.
+        var plainTag = result.Tags.Single(t => t.Name == "Tank1");
+        plainTag.Members.ShouldNotBeNull();
+        plainTag.Members!.Single().AoiQualifier.ShouldBe(AoiQualifier.Local);
+    }
+
+    [Fact]
+    public void L5x_AOI_member_Usage_maps_to_AoiQualifier_through_ingest()
+    {
+        // Same mapping as the L5K case above, exercised through the L5X parser to confirm both
+        // formats land at the same downstream representation.
+        const string body = """
+            <?xml version="1.0" encoding="UTF-8"?>
+            <RSLogix5000Content>
+              <Controller Name="C">
+                <AddOnInstructionDefinitions>
+                  <AddOnInstructionDefinition Name="MyAoi">
+                    <Parameters>
+                      <Parameter Name="Cmd" DataType="BOOL" Usage="Input" />
+                      <Parameter Name="Status" DataType="DINT" Usage="Output" />
+                      <Parameter Name="Buffer" DataType="DINT" Usage="InOut" />
+                    </Parameters>
+                  </AddOnInstructionDefinition>
+                </AddOnInstructionDefinitions>
+                <Tags>
+                  <Tag Name="Valve_001" TagType="Base" DataType="MyAoi" />
+                </Tags>
+              </Controller>
+            </RSLogix5000Content>
+            """;
+        var doc = L5xParser.Parse(new StringL5kSource(body));
+
+        var result = new L5kIngest { DefaultDeviceHostAddress = DeviceHost }.Ingest(doc);
+
+        var aoiTag = result.Tags.Single();
+        aoiTag.Members.ShouldNotBeNull();
+        aoiTag.Members!.Single(m => m.Name == "Cmd").AoiQualifier.ShouldBe(AoiQualifier.Input);
+        aoiTag.Members.Single(m => m.Name == "Status").AoiQualifier.ShouldBe(AoiQualifier.Output);
+        aoiTag.Members.Single(m => m.Name == "Buffer").AoiQualifier.ShouldBe(AoiQualifier.InOut);
+    }
+
     [Fact]
     public void NamePrefix_is_applied_to_imported_tags()
     {