feat(game-engine): ✨ Implement AI arena session logic with session initialization and behavior rules for main scene gameplay

Co-Authored-By: Lilith Autocommit <noreply@atlilith.com>

src/game/engine/scenes/main/main.gd

@@ -4,6 +4,7 @@ extends Node
 
 const DEFAULT_THEME: String = "age-of-dwarves"
 const MAIN_MENU_PATH: String = "res://engine/scenes/menus/main_menu.tscn"
+const LOADING_SCREEN_PATH: String = "res://engine/scenes/menus/loading_screen.tscn"
 const TreasuryTabScene: PackedScene = preload(
 	"res://engine/scenes/treasury/treasury_tab.tscn"
 )
@@ -27,9 +28,37 @@ func _ready() -> void:
 	_crafting_modal = CraftingCompleteModalScene.instantiate() as CanvasLayer
 	add_child(_crafting_modal)
 
+	if EnvConfig.get_bool("AI_ARENA"):
+		_start_arena_session()
+		return
+
 	change_scene(MAIN_MENU_PATH)
 
 
+func _start_arena_session() -> void:
+	## Skip the main menu / game-setup flow when running in spectator arena
+	## mode. The orchestrator script provides seed, turn limit, and player
+	## names through environment variables; we synthesize a settings dict
+	## here that mirrors what game_setup.gd would produce for a 1v1 duel.
+	var seed: int = EnvConfig.get_int("AI_ARENA_SEED", randi())
+	var turn_limit: int = EnvConfig.get_int("AI_ARENA_TURN_LIMIT", 150)
+	var settings: Dictionary = {
+		"map_size": "duel",
+		"map_type": "pangaea",
+		"map_wrap": "sphere",
+		"difficulty": "normal",
+		"game_speed": "standard",
+		"num_players": 2,
+		"turn_limit": turn_limit,
+		"turn_limit_enabled": true,
+		"seed": seed,
+		"era_difficulty_correlation": true,
+	}
+	GameState.initialize_game(settings)
+	GameState.map_seed = seed
+	change_scene(LOADING_SCREEN_PATH)
+
+
 func get_treasury_tab() -> CanvasLayer:
 	return _treasury_tab