fix(windows): #399 preserve legacy MSI install folders

Fall back to the parent directory of the App Paths executable when an
older installer did not write InstallFolder. Keep explicit destinations
and the newer stored folder ahead of the legacy fallback.

Exercise the real MSI searches and actions with isolated per-user probes
on x64 and x86, including legacy paths with spaces and Unicode.

Co-Authored-By: GPT-6 Astra <noreply@openai.com>

.github/workflows/packaging-lint.yml

@@ -71,3 +71,17 @@ jobs:
           EOF
       - name: FreeBSD tarball layout (stub binaries)
         run: bash packaging/freebsd/package.sh --dry-run
+
+  windows-install-folder:
+    runs-on: windows-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - name: Install WiX
+        shell: pwsh
+        run: dotnet tool install --global wix --version 5.0.2
+      - name: Install-folder fallback and precedence (real MSI AppSearch)
+        shell: pwsh
+        run: |
+          ./packaging/windows/test-install-folder.ps1 -Arch x64
+          ./packaging/windows/test-install-folder.ps1 -Arch x86