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.Apps/AllAppsSettings.cs

@@ -0,0 +1,95 @@
+// 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.IO;
+using Microsoft.CmdPal.Ext.Apps.Programs;
+using Microsoft.CmdPal.Ext.Apps.Properties;
+using Microsoft.CommandPalette.Extensions.Toolkit;
+
+namespace Microsoft.CmdPal.Ext.Apps;
+
+public class AllAppsSettings : JsonSettingsManager
+{
+    private static readonly string _namespace = "apps";
+
+    private static string Namespaced(string propertyName) => $"{_namespace}.{propertyName}";
+
+    private static string Experimental(string propertyName) => $"{_namespace}.experimental.{propertyName}";
+
+#pragma warning disable SA1401 // Fields should be private
+    internal static AllAppsSettings Instance = new();
+#pragma warning restore SA1401 // Fields should be private
+
+    public DateTime LastIndexTime { get; set; }
+
+    public List<ProgramSource> ProgramSources { get; set; } = [];
+
+    public List<DisabledProgramSource> DisabledProgramSources { get; set; } = [];
+
+    public List<string> ProgramSuffixes { get; set; } = ["bat", "appref-ms", "exe", "lnk", "url"];
+
+    public List<string> RunCommandSuffixes { get; set; } = ["bat", "appref-ms", "exe", "lnk", "url", "cpl", "msc"];
+
+    public bool EnableStartMenuSource => _enableStartMenuSource.Value;
+
+    public bool EnableDesktopSource => _enableDesktopSource.Value;
+
+    public bool EnableRegistrySource => _enableRegistrySource.Value;
+
+    public bool EnablePathEnvironmentVariableSource => _enablePathEnvironmentVariableSource.Value;
+
+    private readonly ToggleSetting _enableStartMenuSource = new(
+        Namespaced(nameof(EnableStartMenuSource)),
+        Resources.enable_start_menu_source,
+        Resources.enable_start_menu_source,
+        true);
+
+    private readonly ToggleSetting _enableDesktopSource = new(
+        Namespaced(nameof(EnableDesktopSource)),
+        Resources.enable_desktop_source,
+        Resources.enable_desktop_source,
+        true);
+
+    private readonly ToggleSetting _enableRegistrySource = new(
+        Namespaced(nameof(EnableRegistrySource)),
+        Resources.enable_registry_source,
+        Resources.enable_registry_source,
+        false); // This one is very noisy
+
+    private readonly ToggleSetting _enablePathEnvironmentVariableSource = new(
+        Namespaced(nameof(EnablePathEnvironmentVariableSource)),
+        Resources.enable_path_environment_variable_source,
+        Resources.enable_path_environment_variable_source,
+        false); // this one is very VERY noisy
+
+    public double MinScoreThreshold { get; set; } = 0.75;
+
+    internal const char SuffixSeparator = ';';
+
+    internal static string SettingsJsonPath()
+    {
+        string directory = Utilities.BaseSettingsPath("Microsoft.CmdPal");
+        Directory.CreateDirectory(directory);
+
+        // now, the state is just next to the exe
+        return Path.Combine(directory, "settings.json");
+    }
+
+    public AllAppsSettings()
+    {
+        FilePath = SettingsJsonPath();
+
+        Settings.Add(_enableStartMenuSource);
+        Settings.Add(_enableDesktopSource);
+        Settings.Add(_enableRegistrySource);
+        Settings.Add(_enablePathEnvironmentVariableSource);
+
+        // Load settings from file upon initialization
+        LoadSettings();
+
+        Settings.SettingsChanged += (s, a) => this.SaveSettings();
+    }
+}