Add tests for SBOM generation determinism across multiple formats

- Created `StellaOps.TestKit.Tests` project for unit tests related to determinism.
- Implemented `DeterminismManifestTests` to validate deterministic output for canonical bytes and strings, file read/write operations, and error handling for invalid schema versions.
- Added `SbomDeterminismTests` to ensure identical inputs produce consistent SBOMs across SPDX 3.0.1 and CycloneDX 1.6/1.7 formats, including parallel execution tests.
- Updated project references in `StellaOps.Integration.Determinism` to include the new determinism testing library.

src/Concelier/__Libraries/StellaOps.Concelier.Connector.Ghsa/Internal/GhsaCursor.cs

@@ -1,5 +1,6 @@
 using System.Collections.Generic;
 using System.Linq;
+using StellaOps.Concelier.Connector.Common.Cursors;
 using StellaOps.Concelier.Documents;
 
 namespace StellaOps.Concelier.Connector.Ghsa.Internal;
@@ -36,15 +37,8 @@ internal sealed record GhsaCursor(
             document["lastUpdatedExclusive"] = LastUpdatedExclusive.Value.UtcDateTime;
         }
 
-        if (CurrentWindowStart.HasValue)
-        {
-            document["currentWindowStart"] = CurrentWindowStart.Value.UtcDateTime;
-        }
-
-        if (CurrentWindowEnd.HasValue)
-        {
-            document["currentWindowEnd"] = CurrentWindowEnd.Value.UtcDateTime;
-        }
+        new TimeWindowCursorState(CurrentWindowStart, CurrentWindowEnd)
+            .WriteTo(document, startField: "currentWindowStart", endField: "currentWindowEnd");
 
         return document;
     }
@@ -59,12 +53,7 @@ internal sealed record GhsaCursor(
         var lastUpdatedExclusive = document.TryGetValue("lastUpdatedExclusive", out var lastUpdated)
             ? ParseDate(lastUpdated)
             : null;
-        var windowStart = document.TryGetValue("currentWindowStart", out var windowStartValue)
-            ? ParseDate(windowStartValue)
-            : null;
-        var windowEnd = document.TryGetValue("currentWindowEnd", out var windowEndValue)
-            ? ParseDate(windowEndValue)
-            : null;
+        var window = TimeWindowCursorState.FromDocumentObject(document, startField: "currentWindowStart", endField: "currentWindowEnd");
         var nextPage = document.TryGetValue("nextPage", out var nextPageValue) && nextPageValue.IsInt32
             ? Math.Max(1, nextPageValue.AsInt32)
             : 1;
@@ -74,8 +63,8 @@ internal sealed record GhsaCursor(
 
         return new GhsaCursor(
             lastUpdatedExclusive,
-            windowStart,
-            windowEnd,
+            window.LastWindowStart,
+            window.LastWindowEnd,
             nextPage,
             pendingDocuments,
             pendingMappings);