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/AbCipDriverOptions.cs

@@ -153,9 +153,14 @@ public sealed record AbCipTagDefinition(
 ///     (class 0x6C) that would auto-discover member layouts lands as a follow-up PR.
 /// </summary>
 /// <remarks>
-///     <see cref="Description"/> carries the per-member comment from L5K/L5X UDT definitions so
+///     <para><see cref="Description"/> carries the per-member comment from L5K/L5X UDT definitions so
 ///     the OPC UA Variable nodes produced for individual members surface their descriptions too,
-///     not just the top-level tag.
+///     not just the top-level tag.</para>
+///     <para>PR abcip-2.6 — <see cref="AoiQualifier"/> tags AOI parameters as Input / Output /
+///     InOut / Local. Plain UDT members default to <see cref="AoiQualifier.Local"/>. Discovery
+///     groups Input / Output / InOut members under sub-folders so an AOI-typed tag fans out as
+///     <c>Tag/Inputs/...</c>, <c>Tag/Outputs/...</c>, <c>Tag/InOut/...</c> while Local stays at the
+///     UDT root — matching how AOIs visually present in Studio 5000.</para>
 /// </remarks>
 public sealed record AbCipStructureMember(
     string Name,
@@ -163,7 +168,30 @@ public sealed record AbCipStructureMember(
     bool Writable = true,
     bool WriteIdempotent = false,
     int? StringLength = null,
-    string? Description = null);
+    string? Description = null,
+    AoiQualifier AoiQualifier = AoiQualifier.Local);
+
+/// <summary>
+///     PR abcip-2.6 — directional qualifier for AOI parameters. Surfaces the Studio 5000
+///     <c>Usage</c> attribute (<c>Input</c> / <c>Output</c> / <c>InOut</c>) so discovery can group
+///     AOI members into sub-folders and downstream consumers can reason about parameter direction.
+///     Plain UDT members (non-AOI types) default to <see cref="Local"/>, which keeps them at the
+///     UDT root + indicates they are internal storage rather than a directional parameter.
+/// </summary>
+public enum AoiQualifier
+{
+    /// <summary>UDT member or AOI local tag — non-directional, browsed at the parent's root.</summary>
+    Local,
+
+    /// <summary>AOI input parameter — written by the caller, read by the AOI body.</summary>
+    Input,
+
+    /// <summary>AOI output parameter — written by the AOI body, read by the caller.</summary>
+    Output,
+
+    /// <summary>AOI bidirectional parameter — passed by reference, both sides may read/write.</summary>
+    InOut,
+}
 
 /// <summary>
 ///     One L5K-import entry. Either <see cref="FilePath"/> or <see cref="InlineText"/> must be