feat: Implement pipeline hot-rebuild and camera improvements

- Fixes issue #45: Add state property to EffectContext for motionblur/afterimage effects
- Fixes issue #44: Reset camera bounce direction state in reset() method
- Fixes issue #43: Implement pipeline hot-rebuild with state preservation
- Adds radial camera mode for polar coordinate scanning
- Adds afterimage and motionblur effects
- Adds acceptance tests for camera and pipeline rebuild

Closes #43, #44, #45

engine/effects/types.py

@@ -100,6 +100,11 @@ class EffectContext:
         """Get a state value from the context."""
         return self._state.get(key, default)
 
+    @property
+    def state(self) -> dict[str, Any]:
+        """Get the state dictionary for direct access by effects."""
+        return self._state
+
 
 @dataclass
 class EffectConfig: