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/Microsoft.CmdPal.Ext.Bookmark/BookmarkPlaceholderForm.cs

@@ -0,0 +1,109 @@
+// 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 System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using System.Text;
+using System.Text.Json.Nodes;
+using System.Text.RegularExpressions;
+using Microsoft.CmdPal.Ext.Bookmarks.Properties;
+using Microsoft.CommandPalette.Extensions.Toolkit;
+using Windows.System;
+
+namespace Microsoft.CmdPal.Ext.Bookmarks;
+
+internal sealed partial class BookmarkPlaceholderForm : FormContent
+{
+    private static readonly CompositeFormat ErrorMessage = System.Text.CompositeFormat.Parse(Resources.bookmarks_required_placeholder);
+
+    private readonly List<string> _placeholderNames;
+
+    private readonly string _bookmark = string.Empty;
+
+    // TODO pass in an array of placeholders
+    public BookmarkPlaceholderForm(string name, string url, string type)
+    {
+        _bookmark = url;
+        var r = new Regex(Regex.Escape("{") + "(.*?)" + Regex.Escape("}"));
+        var matches = r.Matches(url);
+        _placeholderNames = matches.Select(m => m.Groups[1].Value).ToList();
+        var inputs = _placeholderNames.Select(p =>
+        {
+            var errorMessage = string.Format(CultureInfo.CurrentCulture, ErrorMessage, p);
+            return $$"""
+{
+    "type": "Input.Text",
+    "style": "text",
+    "id": "{{p}}",
+    "label": "{{p}}",
+    "isRequired": true,
+    "errorMessage": "{{errorMessage}}"
+}
+""";
+        }).ToList();
+
+        var allInputs = string.Join(",", inputs);
+
+        TemplateJson = $$"""
+{
+  "$schema": "http://adaptivecards.io/schemas/adaptive-card.json",
+  "type": "AdaptiveCard",
+  "version": "1.5",
+  "body": [
+""" + allInputs + $$"""
+  ],
+  "actions": [
+    {
+      "type": "Action.Submit",
+      "title": "{{Resources.bookmarks_form_open}}",
+      "data": {
+        "placeholder": "placeholder"
+      }
+    }
+  ]
+}
+""";
+    }
+
+    public override CommandResult SubmitForm(string payload)
+    {
+        var target = _bookmark;
+
+        // parse the submitted JSON and then open the link
+        var formInput = JsonNode.Parse(payload);
+        var formObject = formInput?.AsObject();
+        if (formObject == null)
+        {
+            return CommandResult.GoHome();
+        }
+
+        foreach (var (key, value) in formObject)
+        {
+            var placeholderString = $"{{{key}}}";
+            var placeholderData = value?.ToString();
+            target = target.Replace(placeholderString, placeholderData);
+        }
+
+        try
+        {
+            var uri = UrlCommand.GetUri(target);
+            if (uri != null)
+            {
+                _ = Launcher.LaunchUriAsync(uri);
+            }
+            else
+            {
+                // throw new UriFormatException("The provided URL is not valid.");
+            }
+        }
+        catch (Exception ex)
+        {
+            System.Diagnostics.Debug.WriteLine($"Error launching URL: {ex.Message}");
+        }
+
+        return CommandResult.GoHome();
+    }
+}