Deduplicate fighter state lifecycle policies (#36)

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/air_dodge.rs

@@ -3,10 +3,7 @@ use crate::{
         animation::AnimKind,
         state::{
             CollisionContext, EnterContext, FighterState, FighterStateImpl, InterruptContext,
-            UpdateContext, air,
-            fall::FallState,
-            ground::GroundedStateCommon,
-            land::{LandingState, LandingType},
+            UpdateContext, air, fall::FallState, land::LandingType,
         },
     },
     input,
@@ -43,19 +40,7 @@ impl FighterStateImpl for AirDodgeState {
         &mut self,
         state_context: &mut CollisionContext,
     ) -> Option<FighterState> {
-        if let Some(res) = state_context.air_collide_with_stage() {
-            // Adjust translation
-            state_context.translation.0 = res.hit_position - state_context.ecb.get_bottom_point();
-            let grounded_common = GroundedStateCommon {
-                current_line_id: res.line_id,
-            };
-            Some(FighterState::Land(LandingState {
-                grounded_common,
-                landing_type: LandingType::Special,
-            }))
-        } else {
-            None
-        }
+        air::collision_interrupt(state_context, LandingType::Special)
     }
 
     fn on_enter(&mut self, state_context: &mut EnterContext) {