CI / build-and-test (push) Failing after 10m51s
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>