fix(physics): disable playful biomechanics during aggressive ad skips

- Fixed a bug where `humanized_scroll(is_skip=True)` could trigger random 'Doomscroll Corrections' (scrolling backwards) or 'reading pauses'.
- This caused the Anti-Stuck loop for ads to fail because the aggressive skip would occasionally just pause or scroll back into the ad.
- Added strict TDD coverage in `test_physics_humanized.py` to verify `is_skip` generates strictly forward gestures without pauses.

tests/unit/test_physics_humanized.py

@@ -46,3 +46,40 @@ def test_humanized_scroll_speeds(MockInjector):
     # Timing intervals must all be positive
     for t in timing:
         assert t > 0, f"Timing interval must be positive, got {t}"
+
+
+@patch("GramAddict.core.physics.humanized_input.SendEventInjector")
+def test_humanized_scroll_skip_is_strictly_forward(MockInjector):
+    """
+    Ensures that when is_skip=True (e.g. for aggressive ad skipping),
+    the generated gesture is purely forward (bottom to top swipe),
+    and does NOT contain backwards 'Doomscroll corrections' or 
+    biomechanical 'reading pauses'.
+    """
+    mock_injector = MagicMock()
+    MockInjector.get_instance.return_value = mock_injector
+
+    device = MagicMock()
+    device.get_info.return_value = {"displayHeight": 2400, "displayWidth": 1080}
+
+    from GramAddict.core.physics.humanized_input import humanized_scroll
+
+    # Run multiple times to overcome randomness in play_choice / do_correction
+    for _ in range(50):
+        mock_injector.reset_mock()
+        humanized_scroll(device, is_skip=True)
+        
+        args = mock_injector.inject_gesture.call_args
+        points = args[0][0]
+        timing = args[0][1]
+        
+        # In a forward scroll (bottom to top), the Y coordinate must go from a higher number to a lower number.
+        start_y = points[0][1]
+        end_y = points[-1][1]
+        
+        # End Y MUST be less than Start Y (meaning we scrolled down the feed, swiping finger up)
+        assert end_y < start_y, f"Expected end_y ({end_y}) to be < start_y ({start_y}) for a skip."
+        
+        # Verify no long pauses (reading pause adds 0.5s to 2.0s to timing)
+        for t in timing:
+            assert t < 500, "Found a massive pause in a skip gesture, meaning a reading_pause or dwell was incorrectly inserted!"