refactor: split game logic into library + binary entry point

Move the App setup and module declarations from src/main.rs into a new
src/lib.rs that exposes a single pub fn run(). src/main.rs becomes a
three-line entry point that calls bglga::run(). This is the standard
Bevy-book pattern and lets the game logic be consumed as a library
(e.g. for integration tests, headless tooling, or alternate entry
points) without duplicating the App wiring.

Also gate update_tractor_beam_visual with
run_if(any_with_component::<TractorBeam>) so the system only runs while
a boss has an active tractor beam, instead of every Update tick.

src/main.rs

@@ -1,135 +1,3 @@
-use bevy::prelude::*;
-use std::time::Duration;
-
-pub mod components;
-pub mod constants;
-pub mod resources;
-pub mod game_state;
-pub mod player;
-pub mod enemy;
-pub mod bullet;
-pub mod stage;
-pub mod systems;
-pub mod starfield;
-
-use constants::{PLAYER_RESPAWN_DELAY, STARTING_LIVES, WINDOW_HEIGHT, WINDOW_WIDTH};
-use resources::{ // Added StageConfigurations
-    AttackDiveTimer, CurrentStage, EnemySpawnTimer, FormationState, PlayerLives,
-    PlayerRespawnTimer, Score, StageConfigurations,
-};
-use game_state::{
-    cleanup_game_entities, cleanup_game_over_ui, setup_game_over_ui, AppState,
-    setup_start_menu_ui, cleanup_start_menu_ui, start_menu_button_system,
-    handle_restart_input, restart_game_system,
-};
-use resources::RestartPressed;
-use player::{
-    check_player_enemy_collisions, manage_invincibility, move_player, player_shoot,
-    respawn_player, handle_captured_player,
-};
-use enemy::{
-    check_formation_complete, enemy_shoot, is_formation_complete, move_enemies, spawn_enemies,
-    trigger_attack_dives, boss_capture_attack, update_tractor_beam_visual,
-};
-use bullet::{
-    check_bullet_collisions, check_enemy_bullet_player_collisions, move_bullets,
-    move_enemy_bullets,
-};
-use stage::check_stage_clear;
-use systems::{player_exists, player_vulnerable, setup, should_respawn_player, update_window_title, animate_explosion};
-use starfield::scroll_starfield;
-
 fn main() {
-    App::new()
-        .insert_resource(ClearColor(Color::rgb(0.0, 0.0, 0.1)))
-        .add_plugins(DefaultPlugins.set(WindowPlugin {
-            primary_window: Some(Window {
-                title: "BGLGA".into(),
-                resolution: (WINDOW_WIDTH, WINDOW_HEIGHT).into(),
-                resizable: false,
-                ..default()
-            }),
-            ..default()
-        }))
-        // Add states
-        .init_state::<AppState>() // Changed from add_state to init_state
-        // Initialize game resources
-        .insert_resource(EnemySpawnTimer {
-            timer: Timer::new(Duration::from_secs_f32(1.0), TimerMode::Once),
-        })
-        .insert_resource(PlayerLives { count: STARTING_LIVES })
-        .insert_resource(PlayerRespawnTimer {
-            timer: Timer::new(
-                Duration::from_secs_f32(PLAYER_RESPAWN_DELAY),
-                TimerMode::Once,
-            ),
-        })
-        .insert_resource(Score { value: 0 })
-        .insert_resource(CurrentStage {
-            number: 1,
-            waiting_for_clear: false,
-        })
-        .insert_resource(FormationState {
-            formation_complete: false,
-            total_spawned_this_stage: 0,
-            next_slot_index: 0,
-        })
-        .insert_resource(AttackDiveTimer {
-            timer: Timer::new(Duration::from_secs_f32(3.0), TimerMode::Once),
-        })
-        .insert_resource(StageConfigurations::default()) // Use default stages for now
-        .insert_resource(RestartPressed::default())
-        // Add startup systems
-        .add_systems(Startup, setup)
-        // Core game systems
-        .add_systems(
-            Update,
-            (
-                update_window_title,
-                // Enemy and player systems
-                spawn_enemies,
-                move_player.run_if(player_exists),
-                player_shoot.run_if(player_exists),
-                check_player_enemy_collisions.run_if(player_vulnerable),
-                respawn_player.run_if(should_respawn_player),
-                manage_invincibility,
-                handle_captured_player, // New system for handling captured player
-                // Bullet systems
-                move_bullets,
-                check_bullet_collisions,
-                move_enemy_bullets,
-                check_enemy_bullet_player_collisions.run_if(player_vulnerable),
-                // Enemy systems
-                move_enemies,
-                enemy_shoot, // Consider run_if attacking state? (Handled internally for now)
-                boss_capture_attack, // New system for boss tractor beam
-                update_tractor_beam_visual,
-            )
-                .run_if(in_state(AppState::Playing)),
-        )
-        // Formation/Attack/Stage systems (some need specific ordering or run conditions)
-        .add_systems(
-            Update,
-            (
-                check_formation_complete,
-                trigger_attack_dives.run_if(is_formation_complete), // Run only when formation is complete
-                check_stage_clear, // Uses world access, run separately
-            )
-                .chain() // Ensure these run in order if needed, check_formation first
-                .run_if(in_state(AppState::Playing)),
-        )
-        // Starfield runs in all states
-        .add_systems(Update, scroll_starfield)
-        // Explosion animation runs in all states
-        .add_systems(Update, animate_explosion)
-        // UI and state management systems
-        .add_systems(OnEnter(AppState::StartMenu), setup_start_menu_ui)
-        .add_systems(OnExit(AppState::StartMenu), cleanup_start_menu_ui)
-        .add_systems(Update, start_menu_button_system.run_if(in_state(AppState::StartMenu)))
-        .add_systems(OnEnter(AppState::GameOver), setup_game_over_ui)
-        .add_systems(Update, handle_restart_input.run_if(in_state(AppState::GameOver)))
-        .add_systems(Update, restart_game_system.run_if(in_state(AppState::GameOver)))
-        .add_systems(OnExit(AppState::Playing), cleanup_game_entities)
-        .add_systems(OnExit(AppState::GameOver), cleanup_game_over_ui)
-        .run();
+    bglga::run();
 }