Improve memory safety and alignment handling

- Updated `.gitignore` to include `.vscode/` and clarified comments.
- Introduced `SafeHandle` for managing memory alignment and safe access.
- Refactored `UnsafeArray<T>` to add bounds checking and alignment logic.
- Added `IUnsafeHashCollection<T>` for specialized hash-based collections.
- Refactored `UnsafeHashMap<TKey, TValue>` and `UnsafeHashSet<T>` to use `HashMapHelper<TKey>` with alignment support.
- Made `UnsafeSlotMap<T>` methods `readonly` for immutability.
- Enhanced `HashMapHelper<TKey>` with alignment-aware buffer management and validation.
- Updated benchmarks to use `UnsafeArray<Vector256<int>>` and added capacity checks.
- Incremented assembly version to `1.1.3` in `Misaki.HighPerformance.LowLevel.csproj`.
- Updated `Program.cs` to run `CollectionBenchmark` and demonstrate safe disposal handling.

Misaki.HighPerformance.LowLevel/Collections/UnsafeSlotMap.cs

@@ -206,7 +206,7 @@ public unsafe struct UnsafeSlotMap<T> : IUnsafeCollection<T>
     /// <param name="value">When this method returns, contains the element at the specified slot and generation if found; otherwise, the
     /// default value for type <typeparamref name="T"/>.</param>
     /// <returns>true if the element at the specified slot index and generation is found; otherwise, false.</returns>
-    public bool TryGetElementAt(int slotIndex, int generation, out T value)
+    public readonly bool TryGetElementAt(int slotIndex, int generation, out T value)
     {
         if (slotIndex < 0 || slotIndex >= _capacity)
         {
@@ -232,7 +232,7 @@ public unsafe struct UnsafeSlotMap<T> : IUnsafeCollection<T>
     /// <returns>The element of type <see cref="T"/> stored at the specified slot and generation.</returns>
     /// <exception cref="ArgumentOutOfRangeException">Thrown when <paramref name="slotIndex"/> is less than zero or greater than or equal to the capacity.</exception>
     /// <exception cref="InvalidOperationException">Thrown when the specified slot is not occupied or the generation does not match.</exception>
-    public T GetElementAt(int slotIndex, int generation)
+    public readonly T GetElementAt(int slotIndex, int generation)
     {
         if (slotIndex < 0 || slotIndex >= _capacity)
         {