fix(cmdline): make cmdline work without PIL dependency

- Refactor controller to not require importing engine.layers (which imports PIL)
- Add set_effect_chain_ref for external chain registration
- Fix cmdline to use new ref mechanism

cmdline.py

@@ -60,22 +60,22 @@ def local_command(cmd: str) -> str:
             import effects_plugins
             from engine.effects.registry import get_registry
             from engine.effects.chain import EffectChain
+            from engine.effects.controller import set_effect_chain_ref
 
             effects_plugins.discover_plugins()
             registry = get_registry()
             chain = EffectChain(registry)
             chain.set_order(["noise", "fade", "glitch", "firehose"])
 
-            from engine.layers import _effect_chain
-
-            global _effect_chain_ref
-            _effect_chain_ref = chain
+            set_effect_chain_ref(chain)
 
             from engine.effects.controller import handle_effects_command
 
             return handle_effects_command(cmd)
+        except ImportError as e:
+            return f"Error: {e}\n(Try: pip install Pillow)"
         except Exception as e:
-            return f"Error: {type(e).__name__}: {e}\n(Effects require PIL - run with --send or run mainline first)"
+            return f"Error: {type(e).__name__}: {e}"
     if cmd == "/help":
         return AVAILABLE_COMMANDS
     if cmd == "/quit" or cmd == "/exit":