refactor(legacy): Update production imports to use engine.legacy (Phase 3.3)

- engine/effects/__init__.py: Update get_effect_chain() import
- engine/effects/controller.py: Update fallback import path
- engine/pipeline/adapters.py: Update RenderStage and ItemsStage imports
- Tests will be updated in Phase 3.4

engine/pipeline/adapters.py

@@ -65,8 +65,8 @@ class RenderStage(Stage):
     def process(self, data: Any, ctx: PipelineContext) -> Any:
         """Render items to a text buffer."""
         from engine.effects import next_headline
-        from engine.layers import render_firehose, render_ticker_zone
-        from engine.render import make_block
+        from engine.legacy.layers import render_firehose, render_ticker_zone
+        from engine.legacy.render import make_block
 
         items = data or self._items
         w = ctx.params.viewport_width if ctx.params else self._width
@@ -479,7 +479,7 @@ class FontStage(Stage):
         if data is None:
             return None
 
-        from engine.render import make_block
+        from engine.legacy.render import make_block
 
         w = ctx.params.viewport_width if ctx.params else 80