Implement prototype: venue-driven simulation core, scenarios, tests, and playable entrance scene

- Godot 4.3 project scaffold with first-person guard, procedural world,
  interaction HUD, access inspection, radio forms, debug overlay, shift review
- Simulation core: ShiftCoordinator, VenueScenario, EventScheduler, NPCController/FSM,
  AccessVerifier, EscalationManager, RadioSystem, IncidentRecorder,
  ReputationEvaluator, CrowdSystem, EventBus
- Three authored scenarios (Hollywood Blvd building, The Joke Shop, TV studio)
- Custom headless test runner (25 tests) replacing editor-dependent GUT,
  plus GitHub Actions CI
- Documentation workflow live: README, PLAN (tech stack), TODO/DONE, MEMORY

src/game/main.gd

@@ -0,0 +1,11 @@
+extends Node
+## Top-level game entry point. Instantiates the GameManager which owns the world,
+## guard, simulation coordinator, and UI.
+
+const GameManager := preload("res://src/game/game_manager.gd")
+
+func _ready() -> void:
+	var manager := GameManager.new()
+	manager.name = "GameManager"
+	add_child(manager)
+	print("[Step Line] game started")