test: fix Windows encoding test path resolution

The test was using incorrect path calculation (going up too many
directories). Fixed to properly locate apps/backend from tests/ directory.

tests/test_windows_encoding.py

@@ -0,0 +1,40 @@
+"""
+Test Windows encoding configuration for subprocess calls.
+
+This test verifies that the encoding fixes applied to entry point scripts
+work correctly on Windows.
+"""
+
+import subprocess
+import sys
+from pathlib import Path
+
+import pytest
+
+
+@pytest.mark.skipif(sys.platform != "win32", reason="Windows-specific test")
+def test_validate_spec_unicode_output(tmp_path):
+    """Test that validate_spec.py handles Unicode characters on Windows."""
+    spec_dir = tmp_path / "spec"
+    spec_dir.mkdir()
+
+    # Create a spec with Unicode content
+    (spec_dir / "project_index.json").write_text('{"project_type": "test"}', encoding="utf-8")
+
+    # Find the validate_spec.py script
+    # Tests are in /repo_root/tests/, so apps/backend is ../apps/backend
+    script_path = Path(__file__).parent.parent / "apps" / "backend" / "spec" / "validate_spec.py"
+    if not script_path.exists():
+        pytest.skip("validate_spec.py not found")
+
+    # Run validate_spec.py via subprocess
+    result = subprocess.run(
+        [sys.executable, str(script_path), "--spec-dir", str(spec_dir)],
+        capture_output=True,
+        text=True,
+        encoding="utf-8",
+        errors="replace",
+    )
+
+    # Should succeed without encoding errors
+    assert result.returncode == 0