test(domain): providing documents stores the diploma via the ACL then completes the wait (refs #103)

RED: ProvideDocuments now carries the file bytes, stores them against the zaak via
IAclClient before completing the WachtOpDocumenten wait; owner-scoped; best-effort
when no zaak/process exists yet.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

services/domain/Big.Tests/Fakes.cs

@@ -110,4 +110,13 @@ internal sealed class FakeAclClient(Uri? zaakUrl = null) : IAclClient
         ApprovedZaakUrl = zaakUrl;
         return Task.CompletedTask;
     }
+
+    public (Uri ZaakUrl, byte[] Content, string FileName, string ContentType)? StoredDiploma { get; private set; }
+    public static readonly Uri DefaultDocumentUrl = new("http://openzaak/documenten/api/v1/enkelvoudiginformatieobjecten/doc");
+
+    public Task<Uri> StoreDiplomaAsync(Uri zaakUrl, byte[] content, string fileName, string contentType, CancellationToken ct = default)
+    {
+        StoredDiploma = (zaakUrl, content, fileName, contentType);
+        return Task.FromResult(DefaultDocumentUrl);
+    }
 }