fix(ci): setup MSVC for x86 using vswhere + cmd activation for reliable 32-bit builds on windows-2025

The x86 job was failing at "Install dependencies" (uv sync --frozen --compile)
because packages like pyyaml and greenlet have no cp314-win32 wheels for
Python 3.14 and must be built from sdist. This requires the 32-bit MSVC
toolchain (cl.exe etc.) to be active in the environment.

Key problems with prior attempts:
- Hardcoded paths for "2022" broke because windows-2025 now uses VS 2026
  (paths under Microsoft Visual Studio\18\...).
- ilammy/msvc-dev-cmd is Node 20-based and deprecated under Node 24 forcing.
- Env activation in pwsh steps did not reliably propagate to the uv build
  step (GITHUB_ENV + process env issues for native extension builds).

Solution (standard pattern from MS docs, runner-images, and many C++/Python
extension projects on GitHub):
- Use vswhere.exe (official locator, handles any VS version/edition) to
  dynamically find the installation.
- Activate with "amd64_x86" (correct cross for 64-host -> 32-target).
- Verify activation in Setup step logs (where cl + version).
- Export VCVARSALL path.
- For the critical "Install dependencies" step, use shell: cmd and directly
  call "%VCVARSALL%" amd64_x86 right before "uv sync", with verification.
  This ensures the compiler env is active in the exact context where sdist
  builds happen.

Added verification print also in the install step for easier debugging.

This is the minimal, reliable change strictly for the x86 CI fix (no dep
changes elsewhere). All other actions remain pinned.

Author: AAClause

.github/workflows/build_app.yml

@@ -44,9 +44,58 @@ jobs:
         with:
           python-version: 'cpython-3.14-windows-${{ matrix.arch }}-none'
           working-directory: ${{ github.workspace }}/repo
+      - name: Setup MSVC for x86
+        if: matrix.arch == 'x86'
+        shell: pwsh
+        run: |
+          $ErrorActionPreference = 'Stop'
+          $vswhere = "${env:ProgramFiles(x86)}\Microsoft Visual Studio\Installer\vswhere.exe"
+          if (-not (Test-Path $vswhere)) {
+            throw "vswhere.exe not found at $vswhere"
+          }
+          # Use vswhere (the official/recommended way for GitHub runners, handles VS 2022 and 2026+)
+          $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: $vcvarsall"
+
+          # Activate, update *current process* env + export to GITHUB_ENV for next steps.
+          # Also export VCVARSALL path so later steps (or same if needed) can re-activate reliably.
+          cmd /c "`"$vcvarsall`" amd64_x86 && set" | ForEach-Object {
+            if ($_ -match '^(.*?)=(.*)$') {
+              $n = $matches[1]
+              $v = $matches[2]
+              [Environment]::SetEnvironmentVariable($n, $v, 'Process')
+              Add-Content -Path $env:GITHUB_ENV -Value "$n=$v" -Encoding utf8
+            }
+          }
+          [Environment]::SetEnvironmentVariable('VCVARSALL', $vcvarsall, 'Process')
+          Add-Content -Path $env:GITHUB_ENV -Value "VCVARSALL=$vcvarsall" -Encoding utf8
+
+          # Now verify in the *current* pwsh context (will show in this step's logs)
+          Write-Host "=== Verifying 32-bit MSVC (for uv sdist win32 builds) ==="
+          where.exe cl
+          cl 2>&1 | findstr /C:Version || Write-Host "(cl version not shown)"
+          Write-Host "========================================================"
+          Write-Host "MSVC x86 environment applied to current process and exported to GITHUB_ENV"
       - name: Install dependencies
         working-directory: ${{ github.workspace }}/repo
-        run: uv sync --frozen --compile --group build --group test
+        shell: cmd
+        run: |
+          if defined VCVARSALL (
+            echo Re-activating MSVC using %VCVARSALL%
+            call "%VCVARSALL%" amd64_x86
+            echo === Verifying 32-bit MSVC in install step ===
+            where cl
+            cl 2>&1 | findstr /C:Version || echo (no version)
+            echo =============================================
+          )
+          uv sync --frozen --compile --group build --group test
       - name: compile python bytecode
         working-directory: ${{ github.workspace }}/repo
         run: |