feat(simulation): add vision cone with forward/peripheral/blind sectors (#111)

Implement direction-dependent visibility modulation per D-015.
Forward cone (~120 deg) at full range, peripheral (~180 deg each side)
at reduced range, blind spot (~60 deg behind) excluded. Facing component
updated on player movement via facing_from_delta.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/perception/mod.rs

@@ -4,6 +4,10 @@
 
 use bevy_app::prelude::*;
 
+pub mod observer;
+pub mod shadowcast;
+pub mod vision_cone;
+
 /// Perception system plugin
 /// Manages information boundaries and observer snapshots
 pub struct PerceptionPlugin;