Rename the [Ee]xts dir to ext (#38852)

**WARNING:** This PR will probably blow up all in-flight PRs

at some point in the early days of CmdPal, two of us created seperate
`Exts` and `exts` dirs. Depending on what the casing was on the branch
that you checked one of those out from, it'd get stuck like that on your
PC forever.

Windows didn't care, so we never noticed.

But GitHub does care, and now browsing the source on GitHub is basically
impossible.

Closes #38081

src/modules/cmdpal/ext/SamplePagesExtension/SamplePagesCommandsProvider.cs

@@ -0,0 +1,30 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.CommandPalette.Extensions;
+using Microsoft.CommandPalette.Extensions.Toolkit;
+
+namespace SamplePagesExtension;
+
+public partial class SamplePagesCommandsProvider : CommandProvider
+{
+    public SamplePagesCommandsProvider()
+    {
+        DisplayName = "Sample Pages Commands";
+        Icon = new IconInfo("\uE82D");
+    }
+
+    private readonly ICommandItem[] _commands = [
+       new CommandItem(new SamplesListPage())
+       {
+           Title = "Sample Pages",
+           Subtitle = "View example commands",
+       },
+    ];
+
+    public override ICommandItem[] TopLevelCommands()
+    {
+        return _commands;
+    }
+}