Fix run direction not being taken into account when accelerating (Fixes #11)

Fixes #22

Extracts shared grounded collision/friction and airborne movement/landing policies while preserving state-specific behavior. Running fighters now pass `can_walk_off = true` so they can run off platform edges. Includes grounded and airborne hitstun call sites.

Reviewed-on: #36
Co-authored-by: Álex Román Núñez <eirexe@eirteam.moe>

src/fighter/state/mod.rs

@@ -150,6 +150,7 @@ pub struct UpdateContext<'a> {
     pub fighter_attributes: &'a FighterAttributes,
     pub attack_scripts: &'a Assets<FighterAttackScript>,
     pub attack_script_assets: &'a FighterAttackScriptAssets,
+    pub facing_direction: &'a FighterFacingDirection,
 }
 
 impl UpdateContext<'_> {
@@ -290,6 +291,7 @@ impl<'w, 's> FighterFrameQueryItem<'w, 's> {
             fighter_attributes: attributes,
             attack_scripts,
             attack_script_assets,
+            facing_direction: &self.facing_direction
         }
     }
 

src/fighter/state/run.rs

@@ -41,7 +41,7 @@ impl FighterStateImpl for RunState {
         let last_frame = state_context.input.get_last_frame();
         let (accel, target_vel) = state_context
             .fighter_attributes
-            .get_accel_and_target_dashrun(&last_frame, FGi32::ONE);
+            .get_accel_and_target_dashrun(&last_frame, state_context.facing_direction.to_sign());
         let accel = ground::compute_ground_accel(
             accel,
             target_vel,