feat(effects): add entropy parameter to effect plugins

- Add entropy field to EffectConfig (0.0 = calm, 1.0 = chaotic)
- Provide compute_entropy() method in EffectContext for dynamic scoring
- Update Fade, Firehose, Glitch, Noise plugin defaults with entropy values
- Enables finer control: intensity (strength) vs entropy (randomness)

This separates deterministic effect strength from probabilistic chaos, allowing more expressive control in UI panel and presets.

Fixes #32

engine/effects/plugins/fade.py

@@ -5,7 +5,7 @@ from engine.effects.types import EffectConfig, EffectContext, EffectPlugin
 
 class FadeEffect(EffectPlugin):
     name = "fade"
-    config = EffectConfig(enabled=True, intensity=1.0)
+    config = EffectConfig(enabled=True, intensity=1.0, entropy=0.1)
 
     def process(self, buf: list[str], ctx: EffectContext) -> list[str]:
         if not ctx.ticker_height:

engine/effects/plugins/firehose.py

@@ -9,7 +9,7 @@ from engine.terminal import C_DIM, G_DIM, G_LO, RST, W_GHOST
 
 class FirehoseEffect(EffectPlugin):
     name = "firehose"
-    config = EffectConfig(enabled=True, intensity=1.0)
+    config = EffectConfig(enabled=True, intensity=1.0, entropy=0.9)
 
     def process(self, buf: list[str], ctx: EffectContext) -> list[str]:
         firehose_h = config.FIREHOSE_H if config.FIREHOSE else 0

engine/effects/plugins/glitch.py

@@ -6,7 +6,7 @@ from engine.terminal import DIM, G_LO, RST
 
 class GlitchEffect(EffectPlugin):
     name = "glitch"
-    config = EffectConfig(enabled=True, intensity=1.0)
+    config = EffectConfig(enabled=True, intensity=1.0, entropy=0.8)
 
     def process(self, buf: list[str], ctx: EffectContext) -> list[str]:
         if not buf:

engine/effects/plugins/noise.py

@@ -7,7 +7,7 @@ from engine.terminal import C_DIM, G_DIM, G_LO, RST, W_GHOST
 
 class NoiseEffect(EffectPlugin):
     name = "noise"
-    config = EffectConfig(enabled=True, intensity=0.15)
+    config = EffectConfig(enabled=True, intensity=0.15, entropy=0.4)
 
     def process(self, buf: list[str], ctx: EffectContext) -> list[str]:
         if not ctx.ticker_height: