feat(core): add Camera abstraction for viewport scrolling

- Add Camera class with modes: vertical, horizontal, omni, floating
- Refactor scroll.py and demo to use Camera abstraction
- Add vis_offset for horizontal scrolling support
- Add camera_x to EffectContext for effects
- Add pygame window resize handling
- Add HUD effect plugin for demo mode
- Add --demo flag to run demo mode
- Add tests for Camera and vis_offset

tests/test_layers.py

@@ -87,10 +87,26 @@ class TestRenderTickerZone:
 
     def test_returns_list(self):
         """Returns a list of strings."""
-        result, cache = layers.render_ticker_zone([], 0, 10, 80, {}, 0.0)
+        result, cache = layers.render_ticker_zone(
+            [],
+            scroll_cam=0,
+            camera_x=0,
+            ticker_h=10,
+            w=80,
+            noise_cache={},
+            grad_offset=0.0,
+        )
         assert isinstance(result, list)
 
     def test_returns_dict_for_cache(self):
         """Returns a dict for the noise cache."""
-        result, cache = layers.render_ticker_zone([], 0, 10, 80, {}, 0.0)
+        result, cache = layers.render_ticker_zone(
+            [],
+            scroll_cam=0,
+            camera_x=0,
+            ticker_h=10,
+            w=80,
+            noise_cache={},
+            grad_offset=0.0,
+        )
         assert isinstance(cache, dict)