Fix for duplicated dockbands (#46438)

<!-- Enter a brief description/summary of your PR here. What does it
fix/what does it change/how was it tested (even manually, if necessary)?
-->
## Summary of the Pull Request

CommandProviderWrapper.PinDockBand had no duplicate check and it blindly
called .Add() on the settings list every time. This allowed the same
extension to be pinned multiple times to the dock. Once duplicates
existed in settings, LoadTopLevelCommands would faithfully re-create all
of them on every CommandsChanged reload, making edit-mode unpin appear
broken (unpin removes one, reload brings them all back).

 **Fix**
- CommandProviderWrapper.PinDockBand: Check all three band lists
(Start/Center/End) for an existing (ProviderId, CommandId) match before
adding; early-return if already pinned.
- CommandProviderWrapper.LoadTopLevelCommands: Track seen command IDs in
a HashSet when iterating AllPinnedCommands; skip duplicates so they
never materialize in the UI even if present in settings.
  
<!-- Please review the items on the PR checklist before submitting-->
## PR Checklist

- [ ] Closes: #xxx
<!-- - [ ] Closes: #yyy (add separate lines for additional resolved
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)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **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

---------

Co-authored-by: Jiří Polášek <me@jiripolasek.com>

Author: niels9001

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/CommandProviderWrapper.cs

@@ -301,8 +301,19 @@ private void InitializeCommands(
         var dockSettings = settings.DockSettings;
         var allPinnedCommands = dockSettings.AllPinnedCommands;
         var pinnedBandsForThisProvider = allPinnedCommands.Where(c => c.ProviderId == ProviderId);
+
+        // Track which command IDs we've already added to avoid duplicates
+        // from settings that were pinned multiple times.
+        HashSet<string> seenCommandIds = new(bands.Select(b => b.Id));
+
         foreach (var (providerId, commandId) in pinnedBandsForThisProvider)
         {
+            if (!seenCommandIds.Add(commandId))
+            {
+                Logger.LogWarning($"Skipping duplicate pinned dock band command {commandId} for provider {providerId}");
+                continue;
+            }
+
             Logger.LogDebug($"Looking for pinned dock band command {commandId} for provider {providerId}");
 
             // First, try to lookup the command as one of this provider's
@@ -440,6 +451,17 @@ public void PinDockBand(string commandId, IServiceProvider serviceProvider, Dock
     {
         var settingsService = serviceProvider.GetRequiredService<ISettingsService>();
         var settings = settingsService.Settings;
+        var dockSettings = settings.DockSettings;
+
+        // Prevent duplicate pins — check all sections
+        if (dockSettings.StartBands.Any(b => b.CommandId == commandId && b.ProviderId == this.ProviderId) ||
+            dockSettings.CenterBands.Any(b => b.CommandId == commandId && b.ProviderId == this.ProviderId) ||
+            dockSettings.EndBands.Any(b => b.CommandId == commandId && b.ProviderId == this.ProviderId))
+        {
+            Logger.LogDebug($"Dock band '{commandId}' from provider '{this.ProviderId}' is already pinned; skipping.");
+            return;
+        }
+
         var bandSettings = new DockBandSettings
         {
             CommandId = commandId,

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Dock/DockViewModel.cs

@@ -21,6 +21,7 @@ public sealed partial class DockViewModel
     private readonly IContextMenuFactory _contextMenuFactory;
 
     private DockSettings _settings;
+    private bool _isEditing;
 
     public TaskScheduler Scheduler { get; }
 
@@ -52,6 +53,12 @@ public DockViewModel(
 
     private void DockBands_CollectionChanged(object? sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
     {
+        if (_isEditing)
+        {
+            Logger.LogDebug("Skipping DockBands_CollectionChanged during edit mode");
+            return;
+        }
+
         Logger.LogDebug("Starting DockBands_CollectionChanged");
         SetupBands();
         Logger.LogDebug("Ended DockBands_CollectionChanged");
@@ -302,7 +309,12 @@ public void SaveBandOrder()
         _snapshotCenterBands = null;
         _snapshotEndBands = null;
         _snapshotBandViewModels = null;
-        _settingsService.Save();
+
+        // Save without hotReload to avoid triggering SettingsChanged → SetupBands,
+        // which could race with stale DockBands_CollectionChanged work items and
+        // re-add bands that were just unpinned.
+        _settingsService.Save(hotReload: false);
+        _isEditing = false;
         Logger.LogDebug("Saved band order to settings");
     }
 
@@ -317,6 +329,8 @@ public void SaveBandOrder()
     /// </summary>
     public void SnapshotBandOrder()
     {
+        _isEditing = true;
+
         var dockSettings = _settingsService.Settings.DockSettings;
         _snapshotStartBands = dockSettings.StartBands.Select(b => b.Clone()).ToList();
         _snapshotCenterBands = dockSettings.CenterBands.Select(b => b.Clone()).ToList();
@@ -391,6 +405,7 @@ public void RestoreBandOrder()
         _snapshotCenterBands = null;
         _snapshotEndBands = null;
         _snapshotBandViewModels = null;
+        _isEditing = false;
         Logger.LogDebug("Restored band order from snapshot");
     }