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/view/bullet_renderer.gd

@@ -0,0 +1,60 @@
+extends MultiMeshInstance2D
+## Draws the whole bullet field in one draw call.
+##
+## A bullet hell routinely has a thousand bullets on screen. One Node2D each
+## would cost more than the simulation does, so the renderer reads the client's
+## [BulletPool] arrays directly and pushes them into a MultiMesh. The sprite is
+## generated at runtime, so the project needs no art to run.
+
+const TEXTURE_SIZE := 32
+
+var _colors := {
+	SimConfig.KIND_PLAYER_SHOT: Color(0.45, 0.95, 1.0),
+	SimConfig.KIND_ORB: Color(1.0, 0.35, 0.75),
+	SimConfig.KIND_NEEDLE: Color(1.0, 0.85, 0.3),
+	SimConfig.KIND_HEAVY: Color(1.0, 0.45, 0.2),
+}
+
+
+func _ready() -> void:
+	texture = _make_dot_texture()
+	var mm := MultiMesh.new()
+	mm.transform_format = MultiMesh.TRANSFORM_2D
+	mm.use_colors = true
+	var quad := QuadMesh.new()
+	quad.size = Vector2.ONE
+	mm.mesh = quad
+	mm.instance_count = SimConfig.MAX_BULLETS
+	mm.visible_instance_count = 0
+	multimesh = mm
+
+
+## A soft-edged disc with a bright core, so overlapping bullets stay readable.
+func _make_dot_texture() -> ImageTexture:
+	var img := Image.create(TEXTURE_SIZE, TEXTURE_SIZE, false, Image.FORMAT_RGBA8)
+	var centre := Vector2(TEXTURE_SIZE, TEXTURE_SIZE) * 0.5
+	for y in TEXTURE_SIZE:
+		for x in TEXTURE_SIZE:
+			var d := Vector2(x + 0.5, y + 0.5).distance_to(centre) / (TEXTURE_SIZE * 0.5)
+			var alpha := clampf(1.0 - d, 0.0, 1.0)
+			alpha = pow(alpha, 0.6)
+			var core := clampf(1.0 - d * 1.9, 0.0, 1.0)
+			img.set_pixel(x, y, Color(1.0, 1.0, 1.0, alpha).lerp(Color.WHITE, core * 0.8))
+	return ImageTexture.create_from_image(img)
+
+
+func render_pool(pool: BulletPool) -> void:
+	var mm := multimesh
+	var n := 0
+	for i in pool.high_water:
+		if pool.alive[i] == 0:
+			continue
+		if n >= SimConfig.MAX_BULLETS:
+			break
+		# The texture's visible disc is about 80% of the quad, so scale up a
+		# little to make the drawn radius match the radius used for hits.
+		var d: float = pool.radius[i] * 2.5
+		mm.set_instance_transform_2d(n, Transform2D(0.0, Vector2(d, d), 0.0, pool.pos[i]))
+		mm.set_instance_color(n, _colors.get(pool.kind[i], Color.WHITE))
+		n += 1
+	mm.visible_instance_count = n