Separate Engine Core from Game-Specific Logic

[aram-devdocs]

Labels: enhancement, architecture, refactoring
Depends on: #1, #2, #3, #4

Description:
GameSdk mixes engine responsibilities with game-specific logic (tiled maps).

Tasks:

• Extract tiled map logic into separate system
• Create plugin/extension interface
• Separate rendering, input, and game logic concerns
• Implement dependency injection or service locator

Target Architecture:

pub struct Engine {
    renderer: Box<dyn Renderer>,
    input: InputSystem,
    resources: ResourceManager,
}

pub trait GameSystem {
    fn update(&mut self, engine: &mut Engine, dt: f32);
}

[aram-devdocs]

Superseded by ALPHA-F02 (Provider Abstraction Layer) in the alpha roadmap. See #117.