Initial commit: Transcience MVP

Top-down twin-stick bullet-hell, Godot 4.7, server-authoritative dedicated
server with client-side prediction. Clients send input only; the server
resolves every hit for both players and enemies (no PvP).

- SimWorld: whole simulation as plain RefCounted objects (no nodes, no
  physics server), ~0.24ms/tick at peak load -- runs headless for free and
  drives 78 tests in under a second
- BulletPool: struct-of-arrays bullet storage, replicated as spawn/despawn
  events rather than per-tick state
- Emitter framework (Ring/AimedSpread/WallGap/ArcSweep) shared by trash
  enemies and bosses -- a new boss is data in src/content/content.gd, no
  simulation changes
- The Warden of the Fold: stationary 4-phase boss built entirely on that
  format
- Lobby hub with a portal into on-demand dungeon instances; one process
  hosts the hub plus every concurrent dungeon
- Emergency escape: 3s server-owned channel, cancelled by damage
- tools/check.sh, test.sh (GUT), smoke.sh (real server + bot clients over
  ENet), bench.gd; git hooks wired to the same scripts
- docs/ARCHITECTURE.md, NETCODE.md, WORKFLOW.md, ROADMAP.md

src/game.tscn

@@ -0,0 +1,19 @@
+[gd_scene load_steps=5 format=3]
+
+[ext_resource type="Script" path="res://src/view/game_scene.gd" id="1"]
+[ext_resource type="Script" path="res://src/view/world_view.gd" id="2"]
+[ext_resource type="Script" path="res://src/view/bullet_renderer.gd" id="3"]
+[ext_resource type="Script" path="res://src/ui/hud.gd" id="4"]
+
+[node name="Game" type="Node2D"]
+script = ExtResource("1")
+
+[node name="WorldView" type="Node2D" parent="."]
+position = Vector2(640, 360)
+script = ExtResource("2")
+
+[node name="Bullets" type="MultiMeshInstance2D" parent="WorldView"]
+script = ExtResource("3")
+
+[node name="HUD" type="CanvasLayer" parent="."]
+script = ExtResource("4")