[Task] Refactor to follow ECS rather than layered OOP subsystem

[lextpf]

Context

Rift currently follows a layered OOP subsystem architecture around a traditional game loop. Game
owns and coordinates Tilemap, PlayerCharacter, std::vector<NonPlayerCharacter>, ParticleSystem,
TimeManager, SkyRenderer, Editor, and IRenderer.

Plan

• Introduce an entity registry with stable entity IDs.
• Define components for shared actor/gameplay data, likely including:
  • TransformComponent
  • VelocityComponent
  • ElevationComponent
  • SpriteAnimationComponent
  • RenderableComponent
  • ColliderComponent
  • PlayerTag
  • NpcTag
  • PatrolRouteComponent
  • DialogueComponent
  • InputIntentComponent
• Keep global systems/resources such as Tilemap, IRenderer, CameraController, TimeManager,
  GameStateManager, and asset caches outside ECS initially.
• Extract behavior from PlayerCharacter, NonPlayerCharacter, and Game into systems:
  • input system
  • movement system
  • collision system
  • animation system
  • NPC patrol/AI system
  • dialogue interaction system
  • render extraction / sorting system
• Replace Game’s direct player/NPC update/render orchestration with system execution over
  entities.
• Update editor and console paths to address entities/components instead of concrete player/NPC
  containers.
• Update save/load to serialize ECS entity/component data while keeping map/tile serialization
  intact.
• Add focused tests around movement, collision, NPC patrol, dialogue, save/load, and render-order
  extraction to confirm behavior remains unchanged.

Kind of work

Refactor / cleanup

Proposed change

Refactor the runtime actor/gameplay layer toward an ECS architecture while preserving existing
behavior.

Risks

This touches core runtime behavior and could regress almost anything.

Pre-submission checklist

• This is internal engineering work and does not change user-visible behaviour.