[CmdPal] Add stable AutomationIds across XAML for UI testing (#48033)

## Summary

Adds **77 explicit `AutomationProperties.AutomationId`** declarations (4
→ 81, ~20x) to Command Palette XAML so UI-testing tools (WinAppDriver,
FlaUI, winappCli, Appium) can address controls deterministically instead
of falling back to runtime slugs that change every session. Also covers
the `DataTemplate`-generated long tail (search results, file results,
every extension item, every monitor in Dock settings) by binding
`AutomationId` to existing stable model identifiers via `{x:Bind}`.

Headline: a one-line addition to the four CmdPal `ListItem`
`DataTemplate`s now exposes each instance's underlying `Command.Id`
(e.g. `com.microsoft.cmdpal.builtin.calculator`) as its `AutomationId`.
This is the same pattern as web's `<li data-testid={item.id}>`.

## Why

CmdPal today ships with only **4** explicit
`AutomationProperties.AutomationId` declarations across **44** XAML
files (~303 interactive controls). UI tests are forced to fall back to:

- runtime-generated slugs like `itm-12-9dda` that change every CmdPal
restart, or
- regex-parsing the text output of `winappCli ui inspect`, or
- walking the UIA tree client-side and matching by `Name` (localized,
ambiguous when several controls share a label).

## What changed

### Source changes
- **`Microsoft.CmdPal.UI/ExtViews/ListItemsView.xaml`** — bind
`AutomationProperties.AutomationId="{x:Bind Command.Id, Mode=OneWay}"`
on the root of all 4 `ListItem` `DataTemplate`s (single-row, small-grid,
medium-grid, gallery). Covers **every** runtime list item across all
built-in and third-party providers.
- **`Microsoft.CmdPal.UI/Settings/GeneralPage.xaml`** — 14 IDs on
activation hotkey controls, auto-go-home combo, behaviour toggles,
about-section hyperlinks.
- **`Microsoft.CmdPal.UI/Settings/AppearancePage.xaml`** — 19 IDs on
theme/backdrop/colorization, background image controls, 5 sliders,
behaviour toggles.
- **`Microsoft.CmdPal.UI/Settings/DockSettingsPage.xaml`** — 14 IDs on
enable toggle, theme/colorization/backdrop, background image controls,
plus per-monitor data-bound ID using `DisplayName`.
- **`Microsoft.CmdPal.UI/Settings/ExtensionsPage.xaml`** — 4 IDs on
banner/store hyperlinks plus the per-provider `SettingsCard` (data-bound
to the provider's `Id`, e.g. `com.microsoft.cmdpal.builtin.calculator`).
- **`Microsoft.CmdPal.UI/Settings/ExtensionPage.xaml`** — 5 IDs on
provider enable toggle, alias text/activation, fallback rank link.
- **`Microsoft.CmdPal.UI/Settings/ExtensionGalleryItemPage.xaml`** — 5
IDs on install/cancel/copy-command buttons and author/repo/uninstall
links.
- **`Microsoft.CmdPal.UI/Settings/InternalPage.xaml`** — 7 IDs on the
dev-only "Throw exception" and folder/log-opening buttons.
- **`Microsoft.CmdPal.UI/Pages/ShellPage.xaml`** — 1 data-bound ID on
the `CommandTemplate` button (binds to `CommandViewModel.Id`).
- **`Microsoft.CmdPal.UI.ViewModels/ProviderSettingsViewModel.cs`** —
single-line addition exposing the underlying `CommandProviderWrapper.Id`
so the ExtensionsPage template can bind to it.

### Naming convention applied

`CmdPal_<Page>_<Semantic>` PascalCase, with the existing well-known IDs
left untouched to avoid breaking the `modules/cmdpal/*` checklist tests
already referencing them. `Id` / `TestId` suffixes deliberately omitted
(the attribute is already `AutomationId`); control-type suffixes
(`Toggle` / `Button` / `ComboBox`) omitted because the type lives on the
UIA `type` field already.

### Files NOT touched (deferred)

About 5–7 secondary files (`SettingsWindow.xaml`,
`ExtensionGalleryPage.xaml`, `DockControl.xaml`, `DevRibbon.xaml`, deep
style/viewer XAML) — their interactive controls already carry `x:Name`,
which WinUI auto-promotes to `AutomationId` at runtime, so practical
testability is mostly already there. Can be tightened up in a follow-up
PR.

## Risk

- ✅ Zero runtime cost (`AutomationProperties.AutomationId` is metadata
only)
- ✅ Does not affect localization (`AutomationId` is non-localized by
design)
- ✅ Does not affect user-facing accessibility (screen readers consume
`Name` / `AutomationProperties.Name`, untouched)
- ✅ Does not rename any existing ID; `modules/cmdpal/*` tests
referencing `MainSearchBox` / `PrimaryCommandButton` / `ItemsList` /
etc. remain valid
- ✅ All 51 CmdPal XAML files parse as valid XML (PowerShell `[xml]`
round-trip)
- ✅ All `x:Bind` paths verified against the relevant ViewModel types
(`CommandViewModel.Id`, `DockMonitorConfigViewModel.DisplayName`,
`ProviderSettingsViewModel.Id`)

## Validation requested before merge

XAML compilation was attempted locally but blocked by a missing native
NuGet package (`Microsoft.Windows.ImplementationLibrary`) — needs
`tools\build\build-essentials.cmd` to fully restore first. **Reviewer
please run a clean local build of `Microsoft.CmdPal.UI` (or rely on CI)
to confirm the XAML compiler is happy.**

Once built, a quick smoke check:

```powershell
# After CmdPal restart with the new bits installed:
winapp ui search 'CmdPal_'           -w <hwnd> --json  # should list all the new IDs
winapp ui invoke 'CmdPal_AppearancePage_OpenCommandPalette' -w <hwnd>
winapp ui invoke 'com.microsoft.cmdpal.builtin.calculator' -w <hwnd>   # ListItem template binding
```

## Why this matters beyond our tools

This is the same pattern Microsoft's accessibility and WinUI teams
already recommend for any XAML app intended to be automated. It's the
WinUI equivalent of adding `data-testid` in a web app — universally
accepted as low-risk, high-leverage. WinAppDriver, FlaUI, Appium and any
future automation framework all benefit from the same change.