Fix CI: pin pnpm to 10.14.0 to match lockfile generator version

Newer pnpm 10.x may handle optional platform-specific dependencies
differently. Pin to the exact version used to generate the lockfile.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: tomassurin

.github/workflows/tests.yml

@@ -23,7 +23,7 @@ jobs:
       - name: Setup pnpm
         uses: pnpm/action-setup@v4
         with:
-          version: 10
+          version: 10.14.0
 
       - name: Setup Node.js
         uses: actions/setup-node@v4