test(input): inject secure-open failures on the primitive the platform uses (#503)

Two cases prove the failed-secure-open contract by patching
skillspector.input_handler.os.open. _HAS_SECURE_DIR_FD is False on
Windows, so _open_regular_file_no_follow dispatches to
_open_regular_file_from_windows_handle and os.open is never called. The
failure is never injected there: the file is read normally, and both
cases fail while asserting the contract they exist to protect.

Deny both primitives so the failure reaches the dispatcher on either
platform. The Windows stub raises _FileOpenError, which is what the real
helper raises when CreateFileW fails.

Signed-off-by: kevin9327 <kevin9327@users.noreply.github.com>
Co-authored-by: kevin9327 <kevin9327@users.noreply.github.com>

Author: kevin9327

tests/nodes/test_build_context.py

@@ -1471,7 +1471,13 @@ def test_build_context_reports_read_error_without_fake_empty_content(
     def deny_open(*args: object, **kwargs: object) -> int:
         raise PermissionError("sensitive operating-system detail")
 
+    # The secure open dispatches on the platform: POSIX goes through os.open,
+    # Windows through the handle-based helper. Deny both so the failure is
+    # injected wherever the test happens to run.
     monkeypatch.setattr("skillspector.input_handler.os.open", deny_open)
+    monkeypatch.setattr(
+        "skillspector.input_handler._open_regular_file_from_windows_handle", deny_open
+    )
     result = build_context({"skill_path": str(tmp_path)})
 
     assert "broken.py" in result["components"]

tests/unit/test_input_handler.py

@@ -28,6 +28,7 @@
 from skillspector.input_handler import (
     ALLOWED_GIT_HOSTS,
     InputHandler,
+    _FileOpenError,
     _open_regular_file_from_windows_handle,
     _open_regular_file_no_follow,
 )
@@ -236,8 +237,18 @@ def test_resolve_file_open_failure_does_not_create_temp_dir(tmp_path: Path) -> N
     source = tmp_path / "SKILL.md"
     source.write_text("# Skill", encoding="utf-8")
     handler = InputHandler()
+    denied = OSError("denied")
     try:
-        with patch("skillspector.input_handler.os.open", side_effect=OSError("denied")):
+        # The secure open dispatches on the platform: POSIX goes through os.open,
+        # Windows through the handle-based helper. Deny both so the failure is
+        # injected wherever the test happens to run.
+        with (
+            patch("skillspector.input_handler.os.open", side_effect=denied),
+            patch(
+                "skillspector.input_handler._open_regular_file_from_windows_handle",
+                side_effect=_FileOpenError(source, denied),
+            ),
+        ):
             with pytest.raises(ValueError, match="Could not safely open"):
                 handler.resolve(str(source))
         assert handler.temp_dir_for_cleanup() is None