fix(settings-ui): prevent update checks from resetting modules (#50018)

## Summary of the Pull Request

Prevents update checks from resetting enabled module states when
Settings UI holds stale or default general settings.

The update check now sends the existing action-only IPC shape from
`src/settings-ui/Settings.UI/ViewModels/UpdateViewModel.cs`. Runner
handles that command without applying its payload as general settings in
`src/runner/settings_window.cpp`.

## PR Checklist

- [x] Closes: #48907
- [x] **Communication:** Root cause analysis was posted on the linked
issue
- [x] **Tests:** Added/updated and all pass

## Detailed Description of the Pull Request / Additional comments

Previously, `CheckForUpdates()` embedded the complete mutable
`GeneralSettings` object in a custom-action message. Runner then called
`apply_general_settings` on that action payload. If Settings UI had
loaded fallback defaults, merely checking for an update could persist
those defaults and overwrite the user's enabled module choices.

This change:

- sends only `{ "action": { "general": { "action_name":
"check_for_updates" } } }`;
- prevents Runner from treating an update action as a general-settings
update;
- preserves prerelease behavior because changing that setting already
sends normal general-settings IPC before starting the update check; and
- updates
`src/settings-ui/Settings.UI.UnitTests/ViewModelTests/Update.cs` to
verify non-default module states are neither transmitted nor mutated.

No persisted settings schema, localization, documentation, or binary
changes are required.

## Validation Steps Performed

- Built
`src/settings-ui/Settings.UI.UnitTests/Settings.UI.UnitTests.csproj` for
x64 Debug.
- Ran `ViewModelTests.Update` with `vstest.console.exe`: 26 passed.
- Built `src/runner/runner.vcxproj` for x64 Debug.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/runner/settings_window.cpp

@@ -111,7 +111,6 @@ std::optional<std::wstring> dispatch_json_action_to_module(const json::JsonObjec
                 }
                 else if (action == L"check_for_updates")
                 {
-                    apply_general_settings(value);
                     bool expected_isUpdateCheckThreadRunning = false;
                     if (isUpdateCheckThreadRunning.compare_exchange_strong(expected_isUpdateCheckThreadRunning, true))
                     {

src/settings-ui/Settings.UI.UnitTests/ViewModelTests/Update.cs

@@ -58,13 +58,17 @@ namespace ViewModelTests
         }
 
         [TestMethod]
-        public void CheckForUpdatesShouldShowProgressAndSendCurrentSettings()
+        public void CheckForUpdatesShouldShowProgressAndSendActionOnly()
         {
             string sentMessage = null;
             var generalSettings = new GeneralSettings
             {
                 IncludePrereleaseUpdates = true,
             };
+            generalSettings.Enabled.AlwaysOnTop = false;
+            generalSettings.Enabled.FancyZones = false;
+            generalSettings.Enabled.PowerLauncher = true;
+            var settingsBeforeCheck = generalSettings.ToJsonString();
             var viewModel = CreateViewModel(
                 new TestSettingsRepository(generalSettings),
                 new UpdatingSettings(),
@@ -80,9 +84,12 @@ namespace ViewModelTests
             Assert.IsTrue(viewModel.IsActivityVisible);
             Assert.IsFalse(viewModel.CanStartAction);
 
-            var action = JsonSerializer.Deserialize<GeneralSettingsCustomAction>(sentMessage);
-            Assert.IsTrue(action.GeneralSettingsAction.GeneralSettings.IncludePrereleaseUpdates);
-            Assert.AreEqual("check_for_updates", action.GeneralSettingsAction.GeneralSettings.CustomActionName);
+            using var message = JsonDocument.Parse(sentMessage);
+            var generalAction = message.RootElement.GetProperty("action").GetProperty("general");
+            Assert.AreEqual("check_for_updates", generalAction.GetProperty("action_name").GetString());
+            Assert.IsFalse(generalAction.TryGetProperty("enabled", out _));
+            Assert.IsFalse(generalAction.TryGetProperty("include_prerelease_updates", out _));
+            Assert.AreEqual(settingsBeforeCheck, generalSettings.ToJsonString());
         }
 
         [TestMethod]

src/settings-ui/Settings.UI/ViewModels/UpdateViewModel.cs

@@ -6,6 +6,7 @@ using System;
 using System.Diagnostics;
 using System.IO;
 using System.IO.Abstractions;
+using System.Text.Json;
 using System.Threading;
 using ManagedCommon;
 using Microsoft.PowerToys.Settings.UI.Helpers;
@@ -13,6 +14,7 @@ using Microsoft.PowerToys.Settings.UI.Library;
 using Microsoft.PowerToys.Settings.UI.Library.Helpers;
 using Microsoft.PowerToys.Settings.UI.Library.Interfaces;
 using Microsoft.PowerToys.Settings.UI.Library.Utilities;
+using Microsoft.PowerToys.Settings.UI.SerializationContext;
 using Microsoft.UI.Dispatching;
 
 namespace Microsoft.PowerToys.Settings.UI.ViewModels
@@ -314,15 +316,15 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
                 return;
             }
 
-            var generalSettings = _settingsRepository.SettingsConfig;
-            generalSettings.CustomActionName = "check_for_updates";
-            var customAction = new GeneralSettingsCustomAction(new OutGoingGeneralSettings(generalSettings));
+            var checkForUpdatesAction = JsonSerializer.Serialize(
+                ActionMessage.Create("check_for_updates"),
+                SourceGenerationContextContext.Default.ActionMessage);
 
             RequestActivity();
             StartTransientOperation(TransientUpdateOperation.Checking);
             try
             {
-                if (_sendCheckForUpdatesConfigMessage(customAction.ToString()) != 0)
+                if (_sendCheckForUpdatesConfigMessage(checkForUpdatesAction) != 0)
                 {
                     FailTransientOperation(UpdateUIState.NetworkError, "Failed to send the update check request.");
                 }