fix(ci): use vswhere to locate MSVC for x86 on windows-2025 (VS 2026/18 support)

The hardcoded 2022 discovery failed because windows-2025 runners
now use Visual Studio 2026 (paths under Microsoft Visual Studio\18\...).

Proper solution (matching ilammy/msvc-dev-cmd logic and community
practices for GitHub Actions + VS 2022/2026):
- Use vswhere.exe (official locator, handles any VS version/year)
- Find installationPath dynamically
- Activate with amd64_x86 (64-bit host tools for 32-bit target)
- Verify activation (where cl + version) in logs
- Export full env via GITHUB_ENV for uv sdist builds (pyyaml etc.)

This is the standard robust way used across Python/C++ extension
CI on GitHub Windows runners. No external action (avoids Node 20
issues). shell: pwsh for reliable scripting + child cmd for vcvars.

Keeps change strictly to the x86 CI fix.

Author: AAClause

.github/workflows/build_app.yml

@@ -46,29 +46,33 @@ jobs:
           working-directory: ${{ github.workspace }}/repo
       - name: Setup MSVC for x86
         if: matrix.arch == 'x86'
-        shell: cmd
+        shell: pwsh
         run: |
-          @echo off
-          setlocal
-          set "VCVARS="
-          echo Looking for vcvarsall.bat...
-          for /f "delims=" %%f in ('dir /s /b "C:\Program Files*\Microsoft Visual Studio\2022\*\VC\Auxiliary\Build\vcvarsall.bat" 2^>nul') do (
-            set "VCVARS=%%f"
-            goto :found
-          )
-          :found
-          if not defined VCVARS (
-            echo ERROR: vcvarsall.bat not found anywhere under VS 2022
-            dir "C:\Program Files*\Microsoft Visual Studio\2022" 2>&1 | findstr /i "Enterprise Community Professional BuildTools" || echo (no editions visible)
-            exit /b 1
-          )
-          echo Using: %VCVARS%
-          call "%VCVARS%" amd64_x86
-          echo === Verifying 32-bit MSVC toolchain (for uv sdist builds) ===
-          where cl
-          cl 2>&1 | findstr /C:"Version" || echo (no version banner)
-          echo ============================================================
-          set >> %GITHUB_ENV%
+          $ErrorActionPreference = 'Stop'
+          $vswhere = "${env:ProgramFiles(x86)}\Microsoft Visual Studio\Installer\vswhere.exe"
+          if (-not (Test-Path $vswhere)) {
+            throw "vswhere.exe not found at $vswhere"
+          }
+          $installPath = & $vswhere -latest -products * -property installationPath 2>$null | Select-Object -First 1
+          if (-not $installPath) {
+            throw "vswhere did not return an installation path"
+          }
+          $vcvarsall = Join-Path $installPath 'VC\Auxiliary\Build\vcvarsall.bat'
+          if (-not (Test-Path $vcvarsall)) {
+            throw "vcvarsall.bat not found at $vcvarsall (installPath=$installPath)"
+          }
+          Write-Host "Using vcvarsall: $vcvarsall"
+
+          # Activate and verify in a child cmd (prints to logs)
+          cmd /c "`"$vcvarsall`" amd64_x86 && echo === Verifying 32-bit MSVC (for uv sdist win32 builds) === && where cl && cl 2>&1 | findstr /C:Version && echo ============================================"
+
+          # Export environment for subsequent steps
+          cmd /c "`"$vcvarsall`" amd64_x86 && set" | ForEach-Object {
+            if ($_ -match '^(.*?)=(.*)$') {
+              Add-Content -Path $env:GITHUB_ENV -Value "$($matches[1])=$($matches[2])" -Encoding utf8
+            }
+          }
+          Write-Host "MSVC x86 environment exported to GITHUB_ENV"
       - name: Install dependencies
         working-directory: ${{ github.workspace }}/repo
         run: uv sync --frozen --compile --group build --group test