refactor: move effects_plugins to engine/effects/plugins

- Move effects_plugins/ to engine/effects/plugins/
- Update imports in engine/app.py
- Update imports in all test files
- Follows capability-based deps architecture

Closes #27

engine/app.py

@@ -5,7 +5,7 @@ Application orchestrator — pipeline mode entry point.
 import sys
 import time
 
-import effects_plugins
+import engine.effects.plugins as effects_plugins
 from engine import config
 from engine.display import DisplayRegistry
 from engine.effects import PerformanceMonitor, get_registry, set_monitor

engine/effects/plugins/__init__.py

@@ -18,7 +18,7 @@ def discover_plugins():
             continue
 
         try:
-            module = __import__(f"effects_plugins.{module_name}", fromlist=[""])
+            module = __import__(f"engine.effects.plugins.{module_name}", fromlist=[""])
             for attr_name in dir(module):
                 attr = getattr(module, attr_name)
                 if (

tests/test_benchmark.py

@@ -37,8 +37,8 @@ class TestBenchmarkNullDisplay:
         """Effects should meet minimum processing throughput."""
         import time
 
-        from effects_plugins import discover_plugins
         from engine.effects import EffectContext, get_registry
+        from engine.effects.plugins import discover_plugins
 
         discover_plugins()
         registry = get_registry()

tests/test_border_effect.py

@@ -2,8 +2,7 @@
 Tests for BorderEffect.
 """
 
-
-from effects_plugins.border import BorderEffect
+from engine.effects.plugins.border import BorderEffect
 from engine.effects.types import EffectContext
 
 

tests/test_crop_effect.py

@@ -2,8 +2,7 @@
 Tests for CropEffect.
 """
 
-
-from effects_plugins.crop import CropEffect
+from engine.effects.plugins.crop import CropEffect
 from engine.effects.types import EffectContext
 
 

tests/test_glitch_effect.py

@@ -36,7 +36,7 @@ class TestGlitchEffectStability:
 
     def test_glitch_preserves_line_count(self, effect_context, stable_buffer):
         """Glitch should not change the number of lines in buffer."""
-        from effects_plugins.glitch import GlitchEffect
+        from engine.effects.plugins.glitch import GlitchEffect
 
         effect = GlitchEffect()
         result = effect.process(stable_buffer, effect_context)
@@ -50,7 +50,7 @@ class TestGlitchEffectStability:
 
         Note: Effects may add ANSI color codes, so we check VISIBLE length (stripped).
         """
-        from effects_plugins.glitch import GlitchEffect
+        from engine.effects.plugins.glitch import GlitchEffect
 
         effect = GlitchEffect()
 
@@ -69,7 +69,7 @@ class TestGlitchEffectStability:
         Regression test: Previously glitch used \\033[{row};1H which caused
         conflicts with HUD and border rendering.
         """
-        from effects_plugins.glitch import GlitchEffect
+        from engine.effects.plugins.glitch import GlitchEffect
 
         effect = GlitchEffect()
         result = effect.process(stable_buffer, effect_context)
@@ -86,7 +86,7 @@ class TestGlitchEffectStability:
         self, effect_context, stable_buffer
     ):
         """Glitch output should be deterministic given the same random seed."""
-        from effects_plugins.glitch import GlitchEffect
+        from engine.effects.plugins.glitch import GlitchEffect
 
         effect = GlitchEffect()
         effect.config = EffectConfig(enabled=True, intensity=1.0)
@@ -127,9 +127,9 @@ class TestEffectViewportStability:
 
     def test_effect_chain_preserves_dimensions(self):
         """Effect chain should preserve buffer dimensions."""
-        from effects_plugins.fade import FadeEffect
-        from effects_plugins.glitch import GlitchEffect
-        from effects_plugins.noise import NoiseEffect
+        from engine.effects.plugins.fade import FadeEffect
+        from engine.effects.plugins.glitch import GlitchEffect
+        from engine.effects.plugins.noise import NoiseEffect
 
         ctx = EffectContext(
             terminal_width=80,
@@ -152,7 +152,9 @@ class TestEffectViewportStability:
             assert len(buffer) == original_len, (
                 f"{effect.name} changed line count from {original_len} to {len(buffer)}"
             )
-            for i, (orig_w, new_line) in enumerate(zip(original_widths, buffer, strict=False)):
+            for i, (orig_w, new_line) in enumerate(
+                zip(original_widths, buffer, strict=False)
+            ):
                 visible_len = len(strip_ansi(new_line))
                 assert visible_len == orig_w, (
                     f"{effect.name} changed line {i} visible width from {orig_w} to {visible_len}"
@@ -181,7 +183,7 @@ class TestEffectTestMatrix:
                 pytest.skip("Border handled by display")
             else:
                 effect_module = __import__(
-                    f"effects_plugins.{effect_name}",
+                    f"engine.effects.plugins.{effect_name}",
                     fromlist=[f"{effect_name.title()}Effect"],
                 )
                 effect_class = getattr(effect_module, f"{effect_name.title()}Effect")
@@ -213,7 +215,7 @@ class TestEffectTestMatrix:
         """Effects should not use cursor positioning (causes display conflicts)."""
         try:
             effect_module = __import__(
-                f"effects_plugins.{effect_name}",
+                f"engine.effects.plugins.{effect_name}",
                 fromlist=[f"{effect_name.title()}Effect"],
             )
             effect_class = getattr(effect_module, f"{effect_name.title()}Effect")

tests/test_hud.py

@@ -1,11 +1,10 @@
-
 from engine.effects.performance import PerformanceMonitor, set_monitor
 from engine.effects.types import EffectContext
 
 
 def test_hud_effect_adds_hud_lines():
     """Test that HUD effect adds HUD lines to the buffer."""
-    from effects_plugins.hud import HudEffect
+    from engine.effects.plugins.hud import HudEffect
 
     set_monitor(PerformanceMonitor())
 
@@ -51,7 +50,7 @@ def test_hud_effect_adds_hud_lines():
 
 def test_hud_effect_shows_current_effect():
     """Test that HUD displays the correct effect name."""
-    from effects_plugins.hud import HudEffect
+    from engine.effects.plugins.hud import HudEffect
 
     set_monitor(PerformanceMonitor())
 
@@ -80,7 +79,7 @@ def test_hud_effect_shows_current_effect():
 
 def test_hud_effect_shows_intensity():
     """Test that HUD displays intensity percentage."""
-    from effects_plugins.hud import HudEffect
+    from engine.effects.plugins.hud import HudEffect
 
     set_monitor(PerformanceMonitor())
 

tests/test_tint_effect.py

@@ -1,6 +1,6 @@
 import pytest
 
-from effects_plugins.tint import TintEffect
+from engine.effects.plugins.tint import TintEffect
 from engine.effects.types import EffectConfig