fix: add missing shell bash directive to Windows PowerShell steps

- Fix PowerShell syntax error in 'Generate platform test report' step
- Add shell: bash directive to ensure bash syntax works on Windows runners
- Fix 'Generate overall summary' step for consistency
- This resolves the remaining Windows CI failures in Cross-Platform Tests

Author: Mearman

.github/workflows/cross-platform-tests.yml

@@ -280,6 +280,7 @@ jobs:
             echo "❌ **Status:** Some tests failed" >> $GITHUB_STEP_SUMMARY
           fi
           echo "" >> $GITHUB_STEP_SUMMARY
+        shell: bash
 
       - name: Upload test artifacts
         if: always()
@@ -315,4 +316,5 @@ jobs:
           echo "- Windows - Case-insensitive filesystem" >> $GITHUB_STEP_SUMMARY
           echo "- macOS - Case-insensitive filesystem" >> $GITHUB_STEP_SUMMARY
           echo "" >> $GITHUB_STEP_SUMMARY
-          echo "🔧 **Node.js Versions:** 20.x, 22.x" >> $GITHUB_STEP_SUMMARY
+          echo "🔧 **Node.js Versions:** 20.x, 22.x" >> $GITHUB_STEP_SUMMARY
+        shell: bash