Add support for fake input in asciicast recordings

* Fixes a bug with `SelectionPrompt` and page size.
* Allow `IAnsiConsoleInput` to return `null`.

resources/scripts/Generator/Commands/AsciiCast/AnsiConsoleExtensions.cs

@@ -0,0 +1,33 @@
+using System;
+using Spectre.Console;
+using Generator.Commands;
+using System.Threading;
+
+namespace DocExampleGenerator
+{
+    internal static class AnsiConsoleExtensions
+    {
+        /// <summary>
+        /// Displays something via AnsiConsole, waits a bit and then simulates typing based on the input. If the console
+        /// doesn't have the focus this will just type into whatever window does so watch the alt-tab.
+        /// </summary>
+        /// <param name="console"></param>
+        /// <param name="action">The display action.</param>
+        /// <param name="input">The characters to type. ↑ for an up arrow, ↓ for down arrow, ↲ for a return and ¦ for a pause.</param>
+        /// <param name="initialDelayMs">How long to delay before typing. This should be at least 100ms because we won't check if the prompt has displayed before simulating typing.</param>
+        /// <param name="keypressDelayMs">Delay between keypresses. There will be a bit of randomness between each keypress +/- 20% of this value.</param>
+        public static void DisplayThenType(this IAnsiConsole console, Action<IAnsiConsole> action, string input, int initialDelayMs = 500, int keypressDelayMs = 200)
+        {
+            if (console is not AsciiCastConsole asciiConsole)
+            {
+                throw new InvalidOperationException("Not an ASCII cast console");
+            }
+
+            asciiConsole.Input.PushText(input, keypressDelayMs);
+
+            Thread.Sleep(initialDelayMs);
+
+            action(console);
+        }
+    }
+}