Refactor search context struct; add MemSearch cancel tests

Refactored VMMDLL_MEM_SEARCH_CONTEXT to use a fixed-size filler array and removed explicit struct packing. Added unit tests to verify that MemSearch methods correctly throw OperationCanceledException when a canceled CancellationToken is provided.

Author: lone7254

src/VmmSharpEx/Internal/Vmmi.cs

@@ -885,12 +885,11 @@ public struct VMMDLL_MEM_SEARCH_CONTEXT_SEARCHENTRY
     [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
     public delegate bool SearchResultCallback(VMMDLL_MEM_SEARCH_CONTEXT ctx, ulong va, uint iSearch);
 
-    [StructLayout(LayoutKind.Sequential, Pack = 8)]
+    [StructLayout(LayoutKind.Sequential)]
     public unsafe struct VMMDLL_MEM_SEARCH_CONTEXT
     {
         public uint dwVersion;
-        private readonly uint _Filler01;
-        private readonly uint _Filler02;
+        private fixed uint _filler[2];
         public int fAbortRequested;
         public uint cMaxResult;
         public uint cSearch;

src/VmmSharpEx_Tests/CI/VmmSharpEx_VmmSearchTests.cs

@@ -119,4 +119,17 @@ public void VmmSearch_EmptySearch()
         Assert.False(result.IsSuccess);
         Assert.Empty(result.Results);
     }
+
+    [Fact]
+    public async Task VmmSearch_Cancellation()
+    {
+        using var cts = new CancellationTokenSource();
+        cts.Cancel();
+
+        Assert.Throws<OperationCanceledException>(() =>
+            _vmm.MemSearch(_pid, Array.Empty<VmmSearch.SearchItem>(), ct: cts.Token));
+
+        await Assert.ThrowsAsync<OperationCanceledException>(() =>
+            _vmm.MemSearchAsync(_pid, Array.Empty<VmmSearch.SearchItem>(), ct: cts.Token));
+    }
 }