feat(android): align native preview with measured PWA design

scripts/test-integration-evidence.py

@@ -2,6 +2,7 @@
 """Regressions for AGP screenshot output collection, not visual parity tests."""
 import base64
 import importlib.util
+import json
 from pathlib import Path
 import tempfile
 import unittest
@@ -57,6 +58,42 @@ class ScreenshotEvidenceTests(unittest.TestCase):
         self.assertFalse((self.screenshots / image.name).exists())
         self.assertEqual(unrelated.read_text(), "preserve")
 
+    def gallery(self):
+        parent = self.fixture().parent
+        for name in HARNESS.SCREENSHOTS:
+            (parent / name).write_bytes(PNG)
+        (parent / "viewport.json").write_text(json.dumps({"widthPx": 720, "heightPx": 1184, "density": 2}))
+        return parent
+
+    def test_collects_complete_allowlisted_gallery(self):
+        parent = self.gallery()
+        (parent / "private.txt").write_text("not exported")
+        HARNESS.collect_native_screenshot(self.additional, self.screenshots, gallery=True)
+        self.assertEqual({p.name for p in self.screenshots.iterdir()}, set(HARNESS.VISUAL_OUTPUTS))
+
+    def test_partial_gallery_is_not_exported(self):
+        parent = self.gallery()
+        (parent / "notes-dark.png").unlink()
+        with self.assertRaisesRegex(AssertionError, "Missing or ambiguous"):
+            HARNESS.collect_native_screenshot(self.additional, self.screenshots, gallery=True)
+        self.assertFalse(self.screenshots.exists())
+
+    def test_clears_every_known_gallery_file_but_preserves_unrelated(self):
+        parent = self.gallery()
+        HARNESS.collect_native_screenshot(self.additional, self.screenshots, gallery=True)
+        (parent / "other.png").write_bytes(PNG)
+        HARNESS.prepare_android_screenshots(self.output)
+        self.assertEqual([p.name for p in parent.iterdir()], ["other.png"])
+        self.assertEqual(list(self.screenshots.iterdir()), [])
+
+    def test_rejects_gallery_split_across_devices(self):
+        parent = self.gallery()
+        other = parent.with_name("second")
+        other.mkdir()
+        (parent / "notes-dark.png").rename(other / "notes-dark.png")
+        with self.assertRaisesRegex(AssertionError, "Mixed-device"):
+            HARNESS.collect_native_screenshot(self.additional, self.screenshots, gallery=True)
+
 
 if __name__ == "__main__":
     unittest.main()