test: add pytest markers, conftest, fix Windows-incompatible existing tests

- Add tests/conftest.py with deterministic_rng + sample_profile fixtures
- Register unit/integration/e2e markers in pyproject.toml
- Mark existing 14 tests as @pytest.mark.unit
- Fix test_cli.py: use 'invisible_playwright' (underscore) for 'python -m'
- Fix test_translate_includes_gpu_renderer: assert Windows behavior (empty renderer)

tests/test_constants.py

@@ -1,29 +1,35 @@
-from invisible_playwright.constants import BINARY_VERSION, BINARY_BASENAME, ARCHIVE_NAME
+import pytest
+
+from invisible_playwright.constants import ARCHIVE_NAME, BINARY_BASENAME, BINARY_VERSION
 
 
+@pytest.mark.unit
 def test_binary_version_format():
     assert BINARY_VERSION.startswith("firefox-")
     assert BINARY_VERSION.split("-", 1)[1].isdigit()
 
 
+@pytest.mark.unit
 def test_archive_name_windows():
     name = ARCHIVE_NAME("win32", "AMD64")
     assert name.endswith(".zip")
     assert "win-x86_64" in name
 
 
+@pytest.mark.unit
 def test_archive_name_linux():
     name = ARCHIVE_NAME("linux", "x86_64")
     assert name.endswith(".tar.gz")
     assert "linux-x86_64" in name
 
 
+@pytest.mark.unit
 def test_archive_name_unsupported_raises():
-    import pytest
     with pytest.raises(NotImplementedError):
         ARCHIVE_NAME("darwin", "arm64")
 
 
+@pytest.mark.unit
 def test_binary_basename_format():
     assert "firefox" in BINARY_BASENAME.lower()
     assert "stealth" in BINARY_BASENAME.lower()