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

tools/setup_input_map.gd

@@ -0,0 +1,48 @@
+extends SceneTree
+## Writes the project's input map into project.godot.
+##
+## Hand-editing the [input] section is error-prone -- the events are serialised
+## engine objects with a long property list. Generating them through the real
+## API means the file is always in the format the engine expects.
+##
+##   godot --headless --path . --script tools/setup_input_map.gd
+##
+## Re-run after changing the bindings below. Physical keycodes are used so the
+## bindings follow key position rather than layout.
+
+
+func _init() -> void:
+	_action("move_up", [_key(KEY_W), _key(KEY_UP)])
+	_action("move_down", [_key(KEY_S), _key(KEY_DOWN)])
+	_action("move_left", [_key(KEY_A), _key(KEY_LEFT)])
+	_action("move_right", [_key(KEY_D), _key(KEY_RIGHT)])
+	_action("fire", [_mouse(MOUSE_BUTTON_LEFT), _key(KEY_SPACE)])
+	_action("emergency_escape", [_key(KEY_F)])
+	_action("interact", [_key(KEY_E)])
+	var err := ProjectSettings.save()
+	print("input map written, err=%d" % err)
+	quit(0 if err == OK else 1)
+
+
+func _action(name: String, events: Array) -> void:
+	ProjectSettings.set_setting("input/" + name, {
+		"deadzone": 0.2,
+		"events": events,
+	})
+
+
+## device -1 (DEVICE_ID_EMULATION) is what the editor writes and is the only
+## value that matches input from a real device. A freshly constructed event
+## defaults to 16, which silently matches nothing.
+func _key(code: Key) -> InputEventKey:
+	var e := InputEventKey.new()
+	e.device = -1
+	e.physical_keycode = code
+	return e
+
+
+func _mouse(button: MouseButton) -> InputEventMouseButton:
+	var e := InputEventMouseButton.new()
+	e.device = -1
+	e.button_index = button
+	return e