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_prefs.py

@@ -1,14 +1,19 @@
+import pytest
+
 from invisible_playwright._fpforge import generate_profile
 from invisible_playwright.prefs import translate_profile_to_prefs
 
 
-def test_translate_includes_gpu_renderer():
+@pytest.mark.unit
+def test_translate_includes_gpu_renderer_windows():
+    """On Windows, renderer/vendor are cleared so ANGLE reports native hardware."""
     p = generate_profile(seed=42)
     prefs = translate_profile_to_prefs(p)
-    assert prefs["zoom.stealth.webgl.renderer"] == p.gpu.renderer
-    assert prefs["zoom.stealth.webgl.vendor"] == p.gpu.vendor
+    assert prefs["zoom.stealth.webgl.renderer"] == ""
+    assert prefs["zoom.stealth.webgl.vendor"] == ""
 
 
+@pytest.mark.unit
 def test_translate_includes_screen():
     p = generate_profile(seed=42)
     prefs = translate_profile_to_prefs(p)
@@ -16,18 +21,21 @@ def test_translate_includes_screen():
     assert prefs["zoom.stealth.screen.height"] == p.screen.height
 
 
+@pytest.mark.unit
 def test_translate_is_deterministic_per_seed():
     a = translate_profile_to_prefs(generate_profile(seed=42))
     b = translate_profile_to_prefs(generate_profile(seed=42))
     assert a == b
 
 
+@pytest.mark.unit
 def test_translate_varies_across_seeds():
     a = translate_profile_to_prefs(generate_profile(seed=1))
     b = translate_profile_to_prefs(generate_profile(seed=2))
     assert a != b
 
 
+@pytest.mark.unit
 def test_translate_has_stealth_baseline_constants():
     p = generate_profile(seed=42)
     prefs = translate_profile_to_prefs(p)