CmdPal: Add a dock (#45824)

Add support for a "dock" window in CmdPal. The dock is a toolbar powered
by the `APPBAR` APIs. This gives you a persistent region to display
commands for quick shortcuts or glanceable widgets.

The dock can be pinned to any side of the screen.
The dock can be independently styled with any of the theming controls
cmdpal already has
The dock has three "regions" to pin to - the "start", the "center", and
the "end".
Elements on the dock are grouped as "bands", which contains a set of
"items". Each "band" is one atomic unit. For example, the Media Player
extension produces 4 items, but one _band_.
The dock has only one size (for now)
The dock will only appear on your primary display (for now)

This PR includes support for pinning arbitrary top-level commands to the
dock - however, we're planning on replacing that with a more universal
ability to pin any command to the dock or top level. (see #45191). This
is at least usable for now.

This is definitely still _even more preview_ than usual PowerToys
features, but it's more than usable. I'd love to get it out there and
start collecting feedback on where to improve next. I'll probably add a
follow-up issue for tracking the remaining bugs & nits.

closes #45201

---------

Co-authored-by: Niels Laute <niels.laute@live.nl>

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Messages/EnterDockEditModeMessage.cs

@@ -0,0 +1,7 @@
+// 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.
+
+namespace Microsoft.CmdPal.UI.ViewModels.Messages;
+
+public record EnterDockEditModeMessage();

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Messages/NavigateToPageMessage.cs

@@ -4,4 +4,4 @@
 
 namespace Microsoft.CmdPal.UI.ViewModels.Messages;
 
-public record NavigateToPageMessage(PageViewModel Page, bool WithAnimation, CancellationToken CancellationToken);
+public record NavigateToPageMessage(PageViewModel Page, bool WithAnimation, CancellationToken CancellationToken, bool TransientPage = false);

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Messages/PerformCommandMessage.cs

@@ -18,6 +18,8 @@ public record PerformCommandMessage
 
     public bool WithAnimation { get; set; } = true;
 
+    public bool TransientPage { get; set; }
+
     public PerformCommandMessage(ExtensionObject<ICommand> command)
     {
         Command = command;

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Messages/PinToDockMessage.cs

@@ -0,0 +1,7 @@
+// 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.
+
+namespace Microsoft.CmdPal.UI.ViewModels.Messages;
+
+public record PinToDockMessage(string ProviderId, string CommandId, bool Pin);

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Messages/ShowHideDockMessage.cs

@@ -0,0 +1,7 @@
+// 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.
+
+namespace Microsoft.CmdPal.UI.ViewModels.Messages;
+
+public record ShowHideDockMessage(bool ShowDock);

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Messages/UnpinCommandItemMessage.cs

@@ -4,6 +4,4 @@
 
 namespace Microsoft.CmdPal.UI.ViewModels.Messages;
 
-public record UnpinCommandItemMessage(string ProviderId, string CommandId)
-{
-}
+public record UnpinCommandItemMessage(string ProviderId, string CommandId);

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Messages/WindowHiddenMessage.cs

@@ -0,0 +1,7 @@
+// 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.
+
+namespace Microsoft.CmdPal.ViewModels.Messages;
+
+public sealed record WindowHiddenMessage();