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/actors/enemies/enemy_def.gd

@@ -0,0 +1,36 @@
+class_name EnemyDef
+extends Resource
+## Data-only description of a trash enemy. Behaviour is picked from a small set
+## of readable, predictable movements -- players should be able to learn an
+## enemy in one encounter.
+
+enum Move {
+	## Never moves. Pure turret.
+	STATIC,
+	## Slides along a fixed heading, bouncing off the arena edges.
+	DRIFT,
+	## Circles its spawn point at a fixed radius.
+	ORBIT,
+	## Walks straight at the nearest player, slowly.
+	APPROACH,
+	## Keeps a preferred distance from the nearest player.
+	STRAFE,
+}
+
+@export var id: StringName = &"drone"
+@export var display_name: String = "Drone"
+@export var max_hp: int = 40
+@export var radius: float = 14.0
+@export var contact_damage: int = 10
+@export var move: Move = Move.DRIFT
+@export var speed: float = 60.0
+## ORBIT radius, or STRAFE preferred distance.
+@export var move_param: float = 120.0
+## Ticks between direction re-evaluations for APPROACH/STRAFE, so enemies read
+## as deliberate rather than twitchy.
+@export var retarget_interval: int = 30
+## Index the client renderer uses to pick a shape/colour.
+@export var visual: int = 0
+@export var emitters: Array[BulletEmitter] = []
+## The emitter timeline wraps at this many ticks.
+@export var pattern_loop_ticks: int = 240