Windows installer: show a finish page after installing (#198) (#257)

The MSI had no UI, so Windows Installer showed only its basic progress box and closed
without saying the install had worked. It now uses WiX's standard WixUI_Minimal dialogs:
a welcome page with the license (MIT or Apache-2.0, built at packaging time from
LICENSE-MIT and LICENSE-APACHE), progress, and a finish page with an optional
"Launch WordCraft" checkbox. The release and Windows ARM64 workflows install the WiX
UI and Util extensions the build now needs. UpgradeCode and component GUIDs are unchanged.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/release.yml

@@ -150,7 +150,12 @@ jobs:
         run: cargo xtask version set "$WORDCRAFT_VERSION"
       - name: Install WiX
         shell: pwsh
-        run: dotnet tool install --global wix --version 5.0.2
+        run: |
+          $PSNativeCommandUseErrorActionPreference = $true  # stop at the first failing command
+          dotnet tool install --global wix --version 5.0.2
+          # Installer dialogs and the finish page's "Launch WordCraft" (packaging/windows/wordcraft.wxs).
+          wix extension add -g WixToolset.UI.wixext/5.0.2
+          wix extension add -g WixToolset.Util.wixext/5.0.2
       - name: Build, sign, package
         shell: pwsh
         env:

.github/workflows/windows-arm64.yml

@@ -45,7 +45,12 @@ jobs:
           key: windows-arm64-package
       - name: Install WiX
         shell: pwsh
-        run: dotnet tool install --global wix --version 5.0.2
+        run: |
+          $PSNativeCommandUseErrorActionPreference = $true  # stop at the first failing command
+          dotnet tool install --global wix --version 5.0.2
+          # Installer dialogs and the finish page's "Launch WordCraft" (packaging/windows/wordcraft.wxs).
+          wix extension add -g WixToolset.UI.wixext/5.0.2
+          wix extension add -g WixToolset.Util.wixext/5.0.2
       - name: Build and package (unsigned)
         shell: pwsh
         env: