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/ShortcutButton.tscn

@@ -0,0 +1,55 @@
+[gd_scene load_steps=2 format=3 uid="uid://sfb1fw8j6ufu"]
+
+[ext_resource type="Script" uid="uid://k6hvvpekp0xw" path="res://addons/gut/gui/ShortcutButton.gd" id="1"]
+
+[node name="ShortcutButton" type="Control"]
+custom_minimum_size = Vector2(210, 30)
+layout_mode = 3
+anchor_right = 0.123
+anchor_bottom = 0.04
+offset_right = 68.304
+offset_bottom = 6.08
+script = ExtResource("1")
+
+[node name="Layout" type="HBoxContainer" parent="."]
+layout_mode = 0
+anchor_right = 1.0
+anchor_bottom = 1.0
+
+[node name="lblShortcut" type="Label" parent="Layout"]
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 7
+text = "<None>"
+horizontal_alignment = 2
+
+[node name="CenterContainer" type="CenterContainer" parent="Layout"]
+custom_minimum_size = Vector2(10, 0)
+layout_mode = 2
+
+[node name="SetButton" type="Button" parent="Layout"]
+custom_minimum_size = Vector2(60, 0)
+layout_mode = 2
+text = "Set"
+
+[node name="SaveButton" type="Button" parent="Layout"]
+visible = false
+custom_minimum_size = Vector2(60, 0)
+layout_mode = 2
+text = "Save"
+
+[node name="CancelButton" type="Button" parent="Layout"]
+visible = false
+custom_minimum_size = Vector2(60, 0)
+layout_mode = 2
+text = "Cancel"
+
+[node name="ClearButton" type="Button" parent="Layout"]
+custom_minimum_size = Vector2(60, 0)
+layout_mode = 2
+text = "Clear"
+
+[connection signal="pressed" from="Layout/SetButton" to="." method="_on_SetButton_pressed"]
+[connection signal="pressed" from="Layout/SaveButton" to="." method="_on_SaveButton_pressed"]
+[connection signal="pressed" from="Layout/CancelButton" to="." method="_on_CancelButton_pressed"]
+[connection signal="pressed" from="Layout/ClearButton" to="." method="_on_ClearButton_pressed"]