CmdPal: Fix All Apps search result limit default (#45804)

## Summary of the Pull Request

This PR adds a new default option to the All Apps extension settings.

- Adds an explicit "Default (n)" option to the choices list as the
default. This option is not tied to a concrete number of items, allowing
the value to change in the future.
- Fixes backward compatibility for users who installed the extension
when `"0"` was accidentally used as the default search result limit
(d07f40eec3). Existing `"0"` values are now treated as "use default
(10)" instead of producing zero results.
- Renames the intentional "0 results" setting value from `"0"` to
`"none"` so it can be clearly distinguished from the previous accidental
default.
- Moves result-limit parsing from `AllAppsCommandProvider` into
`AllAppsSettings`, exposing a parsed `int?` property instead of a raw
string.
- Adds `IgnoreUnknownValue` to `ChoiceSetSetting` so unrecognized stored
values (such as the old `"0"`) are silently ignored on load, preserving
the initialized default.
- Without this the drop-down value in the adaptive card shows as empty.

<img width="842" height="226" alt="image"
src="https://github.com/user-attachments/assets/ae79f173-2e81-43d8-9103-c548ff6e0dc1"
/>


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## PR Checklist

- [ ] Closes: #xxx
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issues) -->
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
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- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

src/modules/cmdpal/ext/Microsoft.CmdPal.Ext.Apps/AllAppsCommandProvider.cs

@@ -16,6 +16,7 @@ namespace Microsoft.CmdPal.Ext.Apps;
 public partial class AllAppsCommandProvider : CommandProvider
 {
     public const string WellKnownId = "AllApps";
+    internal const int DefaultResultLimit = 10;
 
     public static readonly AllAppsPage Page = new();
 
@@ -44,27 +45,7 @@ public partial class AllAppsCommandProvider : CommandProvider
         PinnedAppsManager.Instance.PinStateChanged += OnPinStateChanged;
     }
 
-    public static int TopLevelResultLimit
-    {
-        get
-        {
-            var limitSetting = AllAppsSettings.Instance.SearchResultLimit;
-
-            if (limitSetting is null)
-            {
-                return 10;
-            }
-
-            var quantity = 10;
-
-            if (int.TryParse(limitSetting, out var result))
-            {
-                quantity = result < 0 ? quantity : result;
-            }
-
-            return quantity;
-        }
-    }
+    public static int TopLevelResultLimit => AllAppsSettings.Instance.SearchResultLimit ?? DefaultResultLimit;
 
     public override ICommandItem[] TopLevelCommands() => [_listItem, .. _page.GetPinnedApps()];
 

src/modules/cmdpal/ext/Microsoft.CmdPal.Ext.Apps/AllAppsSettings.cs

@@ -4,7 +4,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Globalization;
 using System.IO;
+using System.Text;
 using Microsoft.CmdPal.Ext.Apps.Helpers;
 using Microsoft.CmdPal.Ext.Apps.Programs;
 using Microsoft.CmdPal.Ext.Apps.Properties;
@@ -14,16 +16,28 @@ namespace Microsoft.CmdPal.Ext.Apps;
 
 public class AllAppsSettings : JsonSettingsManager, ISettingsInterface
 {
+    // "none" instead of "0": the original default was accidentally "0", so existing
+    // users may have "0" stored. Using "none" lets us distinguish intentional "show
+    // no results" from the old accidental default (which is now treated as "use default").
+    private const string NoneResultLimitValue = "none";
+
+    private static readonly CompositeFormat DefaultLimitItemTitleFormat = CompositeFormat.Parse(Resources.limit_default);
+    private static readonly string DefaultLimitItemTitle = string.Format(
+        CultureInfo.CurrentCulture,
+        DefaultLimitItemTitleFormat.Format,
+        AllAppsCommandProvider.DefaultResultLimit);
+
     private static readonly string _namespace = "apps";
 
     private static string Namespaced(string propertyName) => $"{_namespace}.{propertyName}";
 
     private static readonly List<ChoiceSetSetting.Choice> _searchResultLimitChoices =
     [
-        new ChoiceSetSetting.Choice(Resources.limit_0, "0"),
-        new ChoiceSetSetting.Choice(Resources.limit_1, "1"),
-        new ChoiceSetSetting.Choice(Resources.limit_5, "5"),
-        new ChoiceSetSetting.Choice(Resources.limit_10, "10"),
+        new(DefaultLimitItemTitle, "-1"),
+        new(Resources.limit_0, NoneResultLimitValue),
+        new(Resources.limit_1, "1"),
+        new(Resources.limit_5, "5"),
+        new(Resources.limit_10, "10"),
     ];
 
 #pragma warning disable SA1401 // Fields should be private
@@ -52,9 +66,36 @@ public class AllAppsSettings : JsonSettingsManager, ISettingsInterface
         Namespaced(nameof(SearchResultLimit)),
         Resources.limit_fallback_results_source,
         Resources.limit_fallback_results_source_description,
-        _searchResultLimitChoices);
+        _searchResultLimitChoices)
+    {
+        IgnoreUnknownValue = true,
+    };
 
-    public string SearchResultLimit => _searchResultLimitSource.Value ?? string.Empty;
+    /// <summary>
+    /// Parsed search result limit. Returns <see langword="null"/> when the caller should
+    /// use its own default (unrecognized value, empty, or old stored "0").
+    /// </summary>
+    public int? SearchResultLimit
+    {
+        get
+        {
+            var raw = _searchResultLimitSource.Value ?? string.Empty;
+
+            if (string.Equals(raw, NoneResultLimitValue, StringComparison.Ordinal))
+            {
+                return 0;
+            }
+
+            if (string.IsNullOrWhiteSpace(raw)
+                || !int.TryParse(raw, out var result)
+                || result <= 0) //// <= 0: treats old stored "0" as "use default"
+            {
+                return null;
+            }
+
+            return result;
+        }
+    }
 
     private readonly ToggleSetting _enableStartMenuSource = new(
         Namespaced(nameof(EnableStartMenuSource)),

src/modules/cmdpal/ext/Microsoft.CmdPal.Ext.Apps/Properties/Resources.Designer.cs

@@ -19,7 +19,7 @@ namespace Microsoft.CmdPal.Ext.Apps.Properties {
     // class via a tool like ResGen or Visual Studio.
     // To add or remove a member, edit your .ResX file then rerun ResGen
     // with the /str option, or rebuild your VS project.
-    [global::System.CodeDom.Compiler.GeneratedCodeAttribute("System.Resources.Tools.StronglyTypedResourceBuilder", "17.0.0.0")]
+    [global::System.CodeDom.Compiler.GeneratedCodeAttribute("System.Resources.Tools.StronglyTypedResourceBuilder", "18.0.0.0")]
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
     [global::System.Runtime.CompilerServices.CompilerGeneratedAttribute()]
     internal class Resources {
@@ -204,6 +204,15 @@ namespace Microsoft.CmdPal.Ext.Apps.Properties {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Default ({0}).
+        /// </summary>
+        internal static string limit_default {
+            get {
+                return ResourceManager.GetString("limit_default", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Limit the number of applications returned from the top level.
         /// </summary>

src/modules/cmdpal/ext/Microsoft.CmdPal.Ext.Apps/Properties/Resources.resx

@@ -234,4 +234,8 @@
   <data name="limit_none" xml:space="preserve">
     <value>Unlimited</value>
   </data>
+  <data name="limit_default" xml:space="preserve">
+    <value>Default ({0})</value>
+    <comment>default option; {0} = number of items</comment>
+  </data>
 </root>