ci: limit PR-time CI to one installer per platform

The PR-time CI workflow previously built the full Windows installer
matrix (NSIS x3 + MSI + AppX x3) on every push. That's a lot of
billed minutes for installer packaging that rarely changes.

Now each platform builds one representative installer that non-
developer teammates can grab and try from any PR: NSIS x64 on
Windows (via a new 'nsis-x64' wrapper shortname) and DMG on macOS.
Both platforms specify their target explicitly so the wrapper's
default behavior isn't load-bearing.

The full multi-arch matrix still runs on release-candidate dispatch
where the artifacts actually ship.

Estimated savings: Windows CI job drops from ~11 min to ~4 min, with
proportional reductions in billed compute minutes.

Author: cwillisf

.github/workflows/ci.yml

@@ -84,23 +84,33 @@ jobs:
             media-
       - name: Test
         run: npm run test
-      - name: Build
+      # Each platform builds one representative installer on PR-time CI so non-developer
+      # teammates can grab and try the latest from any PR. The full multi-arch matrix
+      # only runs on release-candidate dispatch where the artifacts actually ship.
+      - name: Build macOS DMG
+        if: matrix.os == 'macos-latest'
         timeout-minutes: 30
         env:
           # TODO: fix whatever is causing excessive memory usage during build
           NODE_OPTIONS: --max-old-space-size=4096
-        run: npm run distDev
+        run: npm run distDev -- --target=dmg
+      - name: Build Windows NSIS x64
+        if: matrix.os == 'windows-latest'
+        timeout-minutes: 30
+        env:
+          NODE_OPTIONS: --max-old-space-size=4096
+        run: npm run distDev -- --target=nsis-x64
       - name: Upload macOS artifacts
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7
         if: matrix.os == 'macos-latest'
         with:
           name: macOS-unsigned
           path: dist/Scratch*.dmg
-      - name: Upload Windows artifacts
+          compression-level: 0
+      - name: Upload Windows NSIS x64
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7
         if: matrix.os == 'windows-latest'
         with:
-          name: Windows-unsigned
-          path: |
-            dist/Scratch*.appx
-            dist/Scratch*.exe
+          name: Windows-NSIS-x64
+          path: "dist/Scratch *x64 Setup.exe"
+          compression-level: 0

scripts/electron-builder-wrapper.js

@@ -135,6 +135,12 @@ const calculateTargets = function (wrapperConfig) {
             name: 'nsis:ia32 nsis:x64 nsis:arm64 msi:x64',
             platform: 'win32'
         },
+        windowsNsisX64: {
+            // Single representative installer for PR-time CI — the smallest build that still
+            // produces something a non-developer teammate can install and try on Windows x64.
+            name: 'nsis:x64',
+            platform: 'win32'
+        },
         linuxAppImage: {
             name: 'appimage',
             platform: 'linux'
@@ -154,7 +160,8 @@ const calculateTargets = function (wrapperConfig) {
             'appx': availableTargets.microsoftStore,
             'nsis': availableTargets.windowsDirectDownload,
             'msi': availableTargets.windowsManagedDeployment,
-            'installers': availableTargets.windowsInstallers
+            'installers': availableTargets.windowsInstallers,
+            'nsis-x64': availableTargets.windowsNsisX64
         };
         const selected = targetsByShortName[wrapperConfig.target];
         if (!selected) {