refactor(installer): split installer UI into its own ui.wxs

Moves the WixUI_Minimal UI and finish-screen launch checkbox out of
main.wxs into a dedicated ui.wxs fragment, referenced from main.wxs via
<UIRef Id='OpenCADStudioUI'>. Keeps the package/feature definition and
the UI concerns in separate files.

Updates the release workflow to compile both .wxs files (candle now
writes per-source .wixobj into a directory) and link both objects.

https://claude.ai/code/session_01DFVSKgViFaxEjZD2KsTdtt

.github/workflows/release.yml

@@ -128,17 +128,24 @@ jobs:
           # filename.
           $exePath  = (Resolve-Path target\release\OpenCADStudio.exe).Path
           $iconPath = (Resolve-Path packaging\windows\AppIcon.ico).Path
-          $wxsPath  = (Resolve-Path packaging\windows\main.wxs).Path
+          # main.wxs holds the package/feature; ui.wxs holds the installer UI
-          $wixObj   = Join-Path $PWD "packaging\windows\main.wixobj"
+          # and finish-screen launch checkbox. Both compile together.
+          $mainWxs  = (Resolve-Path packaging\windows\main.wxs).Path
+          $uiWxs     = (Resolve-Path packaging\windows\ui.wxs).Path
+          # candle writes one .wixobj per source into this directory (the
+          # trailing slash tells it -out is a folder, not a single file).
+          $objDir   = Join-Path $PWD "packaging\windows\"
           $msiPath  = Join-Path $PWD "OpenCADStudio.msi"
           & $candle -arch x64 `
             "-dVersion=$version" `
             "-dSource=$exePath" `
             "-dIcon=$iconPath" `
-            $wxsPath `
+            $mainWxs $uiWxs `
-            -out $wixObj
+            -out $objDir
           if ($LASTEXITCODE -ne 0) { throw "candle failed" }
-          & $light $wixObj -ext WixUIExtension -out $msiPath
+          $mainObj = Join-Path $objDir "main.wixobj"
+          $uiObj   = Join-Path $objDir "ui.wixobj"
+          & $light $mainObj $uiObj -ext WixUIExtension -out $msiPath
           if ($LASTEXITCODE -ne 0) { throw "light failed" }
 
       - name: Sign MSI installer (Azure Trusted Signing)

packaging/windows/main.wxs

@@ -122,35 +122,8 @@
       <ComponentRef Id='ProgramMenuDirComp' />
     </Feature>
 
-    <!--
+    <!-- Installer UI + finish-screen launch checkbox (see ui.wxs). -->
-      Finish-screen "Launch Open CAD Studio" checkbox.
+    <UIRef Id='OpenCADStudioUI' />
-      WIXUI_EXITDIALOGOPTIONALCHECKBOX=1 pre-ticks the checkbox; the Publish
-      below fires the launch action when the user clicks Finish with it checked.
-      WixUI_Minimal shows a minimal wizard (Welcome → Progress → Finish).
-    -->
-    <Property Id='WIXUI_EXITDIALOGOPTIONALCHECKBOXTEXT' Value='Launch Open CAD Studio' />
-    <Property Id='WIXUI_EXITDIALOGOPTIONALCHECKBOX' Value='1' />
-
-    <!--
-      Start the installed exe after the wizard closes.
-      asyncNoWait lets the installer exit cleanly while the app starts.
-    -->
-    <CustomAction
-      Id='LaunchApplication'
-      FileKey='OpenCADStudioEXE'
-      ExeCommand=''
-      Execute='immediate'
-      Return='asyncNoWait'
-      Impersonate='yes' />
-
-    <UI>
-      <UIRef Id='WixUI_Minimal' />
-      <Publish
-        Dialog='ExitDialog'
-        Control='Finish'
-        Event='DoAction'
-        Value='LaunchApplication'>WIXUI_EXITDIALOGOPTIONALCHECKBOX = 1 AND NOT Installed</Publish>
-    </UI>
 
   </Product>
 </Wix>

packaging/windows/ui.wxs

@@ -0,0 +1,45 @@
+<?xml version='1.0' encoding='windows-1252'?>
+<!--
+  Installer UI for the Windows MSI, kept separate from the package/feature
+  definition in main.wxs. Linked in via `<UIRef Id='OpenCADStudioUI' />`
+  there; both files are compiled together by candle and linked by light
+  (which needs `-ext WixUIExtension` for the WixUI_Minimal dialog set).
+
+  Provides:
+    * WixUI_Minimal wizard (Welcome → Progress → Finish).
+    * A pre-ticked "Launch Open CAD Studio" checkbox on the finish screen
+      that starts the freshly installed exe when the user clicks Finish.
+-->
+<Wix xmlns='http://schemas.microsoft.com/wix/2006/wi'>
+  <Fragment>
+    <!--
+      Finish-screen "Launch Open CAD Studio" checkbox.
+      WIXUI_EXITDIALOGOPTIONALCHECKBOX=1 pre-ticks the checkbox; the Publish
+      below fires the launch action when the user clicks Finish with it checked.
+    -->
+    <Property Id='WIXUI_EXITDIALOGOPTIONALCHECKBOXTEXT' Value='Launch Open CAD Studio' />
+    <Property Id='WIXUI_EXITDIALOGOPTIONALCHECKBOX' Value='1' />
+
+    <!--
+      Start the installed exe after the wizard closes. FileKey points at the
+      File defined in main.wxs (light resolves the cross-fragment reference).
+      asyncNoWait lets the installer exit cleanly while the app starts.
+    -->
+    <CustomAction
+      Id='LaunchApplication'
+      FileKey='OpenCADStudioEXE'
+      ExeCommand=''
+      Execute='immediate'
+      Return='asyncNoWait'
+      Impersonate='yes' />
+
+    <UI Id='OpenCADStudioUI'>
+      <UIRef Id='WixUI_Minimal' />
+      <Publish
+        Dialog='ExitDialog'
+        Control='Finish'
+        Event='DoAction'
+        Value='LaunchApplication'>WIXUI_EXITDIALOGOPTIONALCHECKBOX = 1 AND NOT Installed</Publish>
+    </UI>
+  </Fragment>
+</Wix>