Add project files, tests, and documentation for GitHub release

- CLI with visible, invisible, all, metadata, and batch commands
- Gemini watermark removal via reverse alpha blending
- Invisible watermark removal via diffusion regeneration (SynthID, TreeRing)
- AI metadata stripping (EXIF, PNG text, C2PA)
- Face protection (YOLO/Haar) and analog humanizer
- 137 tests covering all CLI modes and core engines
- Ruff and Pyright clean

tests/test_platform.py

@@ -0,0 +1,165 @@
+"""Tests for cross-platform and cross-device compatibility.
+
+Verifies that device detection, MPS fallback, and platform-specific
+code paths work correctly on CPU, MPS (macOS), and CUDA (Linux/Windows).
+"""
+
+from __future__ import annotations
+
+from unittest.mock import patch
+
+import pytest
+
+from remove_ai_watermarks.noai.progress import is_mps_error
+from remove_ai_watermarks.noai.utils import get_image_format, is_supported_format
+from remove_ai_watermarks.noai.watermark_profiles import (
+    detect_model_profile,
+    get_model_id_for_profile,
+    get_recommended_strength,
+)
+from remove_ai_watermarks.noai.watermark_remover import get_device, is_watermark_removal_available
+
+# ── Device detection ────────────────────────────────────────────────
+
+
+class TestDeviceDetection:
+    """Tests for get_device() across platforms."""
+
+    def test_returns_valid_device(self):
+        device = get_device()
+        assert device in ("cpu", "mps", "cuda")
+
+    def test_cpu_fallback_when_no_gpu(self):
+        """On CI / machines without GPU, should fall back to cpu or mps."""
+        device = get_device()
+        # Just verify it doesn't crash and returns a valid string
+        assert isinstance(device, str)
+
+    @patch("remove_ai_watermarks.noai.watermark_remover._HAS_TORCH", False)
+    def test_no_torch_returns_cpu(self):
+        assert get_device() == "cpu"
+
+
+class TestMpsErrorDetection:
+    """Tests for MPS error detection helper."""
+
+    def test_detects_mps_error(self):
+        err = RuntimeError("MPS backend out of memory")
+        assert is_mps_error(err) is True
+
+    def test_non_mps_error(self):
+        err = RuntimeError("CUDA out of memory")
+        assert is_mps_error(err) is False
+
+    def test_generic_error(self):
+        err = RuntimeError("something went wrong")
+        assert is_mps_error(err) is False
+
+
+# ── Model profiles ──────────────────────────────────────────────────
+
+
+class TestModelProfiles:
+    """Tests for watermark_profiles.py."""
+
+    def test_default_profile(self):
+        assert get_model_id_for_profile("default") == "Lykon/dreamshaper-8"
+
+    def test_ctrlregen_profile(self):
+        assert get_model_id_for_profile("ctrlregen") == "yepengliu/ctrlregen"
+
+    def test_unknown_profile_raises(self):
+        with pytest.raises(ValueError, match="Unknown model profile"):
+            get_model_id_for_profile("nonexistent")
+
+    def test_detect_default(self):
+        assert detect_model_profile("Lykon/dreamshaper-8") == "default"
+
+    def test_detect_ctrlregen(self):
+        assert detect_model_profile("yepengliu/ctrlregen") == "ctrlregen"
+
+    def test_recommended_strength_high(self):
+        assert get_recommended_strength("treering") == 0.7
+
+    def test_recommended_strength_low(self):
+        assert get_recommended_strength("stablesignature") == 0.04
+
+    def test_recommended_strength_medium(self):
+        assert get_recommended_strength("unknown_type") == 0.35
+
+
+# ── Format utilities ────────────────────────────────────────────────
+
+
+class TestFormatUtils:
+    """Tests for utils.py format helpers."""
+
+    def test_supported_png(self, tmp_path):
+        assert is_supported_format(tmp_path / "test.png")
+
+    def test_supported_jpg(self, tmp_path):
+        assert is_supported_format(tmp_path / "test.jpg")
+
+    def test_supported_jpeg(self, tmp_path):
+        assert is_supported_format(tmp_path / "test.jpeg")
+
+    def test_supported_webp(self, tmp_path):
+        assert is_supported_format(tmp_path / "test.webp")
+
+    def test_unsupported_bmp(self, tmp_path):
+        assert not is_supported_format(tmp_path / "test.bmp")
+
+    def test_unsupported_gif(self, tmp_path):
+        assert not is_supported_format(tmp_path / "test.gif")
+
+    def test_get_format_png(self, tmp_path):
+        assert get_image_format(tmp_path / "x.png") == "PNG"
+
+    def test_get_format_jpg(self, tmp_path):
+        assert get_image_format(tmp_path / "x.jpg") == "JPEG"
+
+    def test_get_format_jpeg(self, tmp_path):
+        assert get_image_format(tmp_path / "x.jpeg") == "JPEG"
+
+    def test_get_format_webp_defaults_png(self, tmp_path):
+        # .webp falls through to PNG in current implementation
+        assert get_image_format(tmp_path / "x.webp") == "PNG"
+
+
+# ── Availability checks ────────────────────────────────────────────
+
+
+class TestAvailability:
+    """Tests for dependency availability checks."""
+
+    def test_watermark_removal_available(self):
+        # In dev env with torch+diffusers installed
+        assert is_watermark_removal_available() is True
+
+    def test_invisible_is_available(self):
+        from remove_ai_watermarks.invisible_engine import is_available
+
+        assert is_available() is True
+
+
+# ── Platform-specific path handling ─────────────────────────────────
+
+
+class TestPlatformPaths:
+    """Verify path handling works on current platform."""
+
+    def test_pathlib_works_for_assets(self):
+        from pathlib import Path
+
+        asset_dir = Path(__file__).parent.parent / "src" / "remove_ai_watermarks" / "assets"
+        assert (asset_dir / "gemini_bg_48.png").exists()
+        assert (asset_dir / "gemini_bg_96.png").exists()
+
+    def test_asset_loading_works(self):
+        """Verify embedded assets load correctly (critical for packaging)."""
+        from remove_ai_watermarks.gemini_engine import GeminiEngine
+
+        engine = GeminiEngine()
+        # If we get here without error, asset loading works
+        assert engine._alpha_small.shape == (48, 48)
+        assert engine._alpha_large.shape == (96, 96)