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

scenes/main.tscn

@@ -0,0 +1,6 @@
+[gd_scene load_steps=2 format=3 uid="uid://bstepmain00000"]
+
+[ext_resource type="Script" path="res://src/game/main.gd" id="1"]
+
+[node name="Main" type="Node"]
+script = ExtResource("1")