Windows installer: refuse Windows 7 and 8 with a clear message (#2310) (#3261)

The Rust standard library has needed Windows 10 since 1.78, so on
Windows 7 and 8 PhotoCraft fails at launch with "The procedure entry
point ProcessPrng could not be located in the dynamic link library
bcryptprimitives.dll" (#2310). The MSI installed anyway.

It now has a launch condition: a registry search sets WINDOWS10ORLATER
from HKLM\...\Windows NT\CurrentVersion\CurrentMajorVersionNumber,
which exists only from Windows 10 on (in the 32- and 64-bit views), and
without it the installer stops with "PhotoCraft needs Windows 10 or
later." Repair and uninstall still run (Installed). MSI's VersionNT
isn't used: it has reported both 603 and 1000 on Windows 10.

The README's Windows downloads now say Windows 10 or later is required;
the portable zip can't check, as Windows rejects the exe before any of
its code runs.

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

README.md

@@ -331,6 +331,8 @@ sha256-verified. Fetch them with `cargo xtask corpus --all` and run the tests wi
 | arm64 (Snapdragon and other ARM PCs) | `photocraft-<ver>-windows-arm64.msi` | `photocraft-<ver>-windows-arm64-portable.zip` |
 | x86 (32-bit) | `photocraft-<ver>-windows-x86.msi` | `photocraft-<ver>-windows-x86-portable.zip` |
 
+Windows 10 or later is required. On Windows 7 and 8 the app can't start (the installer says so).
+
 Installers and executables are code-signed.
 
 ### macOS

packaging/windows/photocraft.en-us.wxl

@@ -7,5 +7,6 @@
   <String Id="WelcomeDlgTitle" Value="{\WixUI_Font_Bigger}Welcome to the [ProductName] [PhotocraftVersion] Setup Wizard" />
   <String Id="WelcomeDlgDescription" Value="The Setup Wizard will install [ProductName] version [PhotocraftVersion] on your computer. Click Next to continue or Cancel to exit the Setup Wizard." />
   <String Id="VerifyReadyDlgInstallTitle" Value="{\WixUI_Font_Title}Ready to install [ProductName] [PhotocraftVersion]" />
+  <String Id="RequiresWindows10" Value="PhotoCraft needs Windows 10 or later. This version of Windows can't run it." />
   <String Id="ExitDialogTitle" Value="{\WixUI_Font_Bigger}Completed the [ProductName] [PhotocraftVersion] Setup Wizard" />
 </WixLocalization>

packaging/windows/photocraft.wxs

@@ -31,6 +31,18 @@
         DowngradeErrorMessage="A newer version of PhotoCraft is already installed." />
     <MediaTemplate EmbedCab="yes" CompressionLevel="high" />
 
+    <!-- Windows 10 or later. The Rust standard library has needed it since 1.78: on Windows 7 and
+         8 the app fails at launch with "The procedure entry point ProcessPrng could not be located
+         in bcryptprimitives.dll" (#2310), so the installer says so instead of installing it.
+         `CurrentMajorVersionNumber` exists only from Windows 10 on, in the 32- and 64-bit
+         registry views alike; MSI's own VersionNT has reported both 603 and 1000 there.
+         `Installed` keeps repair and uninstall working on any Windows. -->
+    <Property Id="WINDOWS10ORLATER" Secure="yes">
+      <RegistrySearch Id="WindowsMajorVersion" Root="HKLM" Key="SOFTWARE\Microsoft\Windows NT\CurrentVersion"
+          Name="CurrentMajorVersionNumber" Type="raw" />
+    </Property>
+    <Launch Condition="Installed OR WINDOWS10ORLATER" Message="!(loc.RequiresWindows10)" />
+
     <!-- MSI caches this icon using its Id as the filename. Advertised shortcuts to an
          .exe need an .exe icon identifier (ICE50), even when the source is an ICO. -->
     <Icon Id="PhotocraftIcon.exe" SourceFile="$(var.IconPath)" />