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

addons/gut/gui/update_required.tscn

@@ -0,0 +1,17 @@
+[gd_scene format=3 uid="uid://sduiv3grt5h4"]
+
+[ext_resource type="Script" uid="uid://bpj4k0w6ft550" path="res://addons/gut/gui/update_required.gd" id="1_rmy01"]
+
+[node name="UpdateRequired" type="AcceptDialog" unique_id=125541884]
+oversampling_override = 1.0
+title = "Invalid GUT Version"
+position = Vector2i(0, 36)
+size = Vector2i(600, 300)
+visible = true
+exclusive = false
+ok_button_text = "Continue"
+script = ExtResource("1_rmy01")
+
+[connection signal="canceled" from="." to="." method="_on_canceled"]
+[connection signal="close_requested" from="." to="." method="_on_close_requested"]
+[connection signal="confirmed" from="." to="." method="_on_confirmed"]