Initial draft of actor runtime abstractions (#197)

* Initial draft of actor runtime abstractions

dotnet/src/Microsoft.Extensions.AI.Agents.Runtime.Abstractions/RemoveKeyOperation.cs

@@ -0,0 +1,23 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System.Text.Json.Serialization;
+
+namespace Microsoft.Extensions.AI.Agents.Runtime;
+
+/// <summary>
+/// Represents an operation to remove a key from an actor's state.
+/// </summary>
+/// <param name="Key">The key to remove from the actor's state.</param>
+public sealed class RemoveKeyOperation(string Key) : ActorStateWriteOperation
+{
+    /// <summary>
+    /// Gets the key for the state operation.
+    /// </summary>
+    [JsonPropertyName("key")]
+    public string Key { get; } = Key;
+
+    /// <summary>
+    /// Gets the type of the write operation.
+    /// </summary>
+    public override ActorWriteOperationType Type => ActorWriteOperationType.RemoveKey;
+}