Expose RelatedCurrencyManager.UseParentCurrentChanged to CargoWise + unit tests

[Copilot]

The BindingContext list-manager storage is now a Dictionary<HashKey, WeakReference> in .NET 10, making CargoWise's ZBindingContext reflection hack (which swapped RelatedCurrencyManager's parent event subscription from CurrentItemChanged → CurrentChanged) non-viable. The base branch already added the opt-in static RelatedCurrencyManager.UseParentCurrentChanged; this PR wires it up for external consumption and validates it.

Changes

• AssemblyInfo.cs — Adds a placeholder InternalsVisibleTo("WiseTech.CargoWise") entry so the CargoWise assembly can set RelatedCurrencyManager.UseParentCurrentChanged. Includes a // TODO: comment requiring the real assembly name and strong-name PublicKey= to be confirmed before merge.

• RelatedCurrencyManager.cs — Expands the XML docs on UseParentCurrentChanged to clarify event semantics (CurrentItemChanged fires on both position changes and item-property edits; CurrentChanged fires only on position changes) and adds a concrete ZBindingContext usage example:

  public class ZBindingContext : BindingContext
  {
      public ZBindingContext()
      {
          // .NET 10 replacement for the old reflection hack
          RelatedCurrencyManager.UseParentCurrentChanged = true;
      }
  }

• RelatedCurrencyManagerTests.cs (new) — Seven tests covering: default value is false; default mode refreshes child on CurrentItemChanged-only trigger (BindingList.ResetItem); opt-in mode suppresses that refresh; both modes refresh on position change; no double subscription from cache hits; rebind unwires cleanly with no stale subscription. All tests save/restore the process-wide static in try/finally.

Open item

The InternalsVisibleTo entry needs the real CargoWise assembly name and strong-name public key before this is production-ready. A key-less entry (any assembly named WiseTech.CargoWise can access internals) is acceptable only for a draft.