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/ui/hud.gd

@@ -0,0 +1,114 @@
+extends CanvasLayer
+## Heads-up display. Built in code rather than as a scene because every element
+## is data-driven -- there is no layout here a designer would want to drag.
+
+const MARGIN := 24.0
+const BAR_W := 260.0
+const BAR_H := 16.0
+
+var _canvas: Control
+var _status: Label
+var _hint: Label
+var _hit_flash: float = 0.0
+var client: ClientRuntime = null
+
+
+func _ready() -> void:
+	layer = 10
+	_canvas = Control.new()
+	_canvas.set_anchors_preset(Control.PRESET_FULL_RECT)
+	_canvas.mouse_filter = Control.MOUSE_FILTER_IGNORE
+	_canvas.draw.connect(_draw_hud)
+	add_child(_canvas)
+
+	_status = _make_label(Vector2(MARGIN, MARGIN))
+	_hint = _make_label(Vector2(MARGIN, 0.0))
+	_hint.set_anchors_preset(Control.PRESET_BOTTOM_LEFT)
+	_hint.position = Vector2(MARGIN, -56.0)
+
+
+func _make_label(pos: Vector2) -> Label:
+	var l := Label.new()
+	l.position = pos
+	l.add_theme_font_size_override("font_size", 14)
+	l.add_theme_color_override("font_color", Color(0.8, 0.85, 0.95))
+	_canvas.add_child(l)
+	return l
+
+
+func _process(delta: float) -> void:
+	client = Net.client
+	_hit_flash = maxf(_hit_flash - delta * 2.5, 0.0)
+	_status.text = _status_text()
+	_hint.text = _hint_text()
+	_canvas.queue_redraw()
+
+
+func _status_text() -> String:
+	if client == null:
+		return "connecting..."
+	var where := "LOBBY" if client.instance_kind == Protocol.InstanceKind.LOBBY else "DUNGEON"
+	return "%s  instance %d   hp %d/%d   %d fps" % [
+		where, client.instance_id, client.my_hp, SimConfig.PLAYER_MAX_HP,
+		Engine.get_frames_per_second()]
+
+
+func _hint_text() -> String:
+	if client == null:
+		return ""
+	if client.instance_kind == Protocol.InstanceKind.LOBBY:
+		return "WASD move   mouse aim   LMB fire   E on the ring to enter a dungeon"
+	return "WASD move   mouse aim   LMB fire   hold F to escape to the lobby"
+
+
+func _draw_hud() -> void:
+	if client == null:
+		return
+	var origin := Vector2(MARGIN, MARGIN + 28.0)
+	_bar(origin, float(client.my_hp) / float(SimConfig.PLAYER_MAX_HP),
+		Color(0.35, 0.9, 0.6), Color(0.1, 0.15, 0.18))
+
+	if client.my_escaping:
+		_bar(origin + Vector2(0.0, BAR_H + 8.0), client.my_escape,
+			Color(0.5, 0.85, 1.0), Color(0.1, 0.15, 0.2))
+		_canvas.draw_string(ThemeDB.fallback_font,
+			origin + Vector2(BAR_W + 12.0, BAR_H + 8.0 + BAR_H),
+			"ESCAPING", HORIZONTAL_ALIGNMENT_LEFT, -1, 14, Color(0.5, 0.85, 1.0))
+
+	_draw_boss_bar()
+
+	if not client.my_alive:
+		var size := _canvas.size
+		_canvas.draw_string(ThemeDB.fallback_font, size * 0.5 - Vector2(70.0, 0.0),
+			"DOWN -- respawning", HORIZONTAL_ALIGNMENT_LEFT, -1, 22, Color(1.0, 0.4, 0.4))
+
+	if _hit_flash > 0.0:
+		_canvas.draw_rect(Rect2(Vector2.ZERO, _canvas.size),
+			Color(1.0, 0.2, 0.25, 0.18 * _hit_flash))
+
+
+func _draw_boss_bar() -> void:
+	var b := client.boss_state()
+	if b.is_empty() or client.boss_def == null:
+		return
+	var w := 560.0
+	var pos := Vector2((_canvas.size.x - w) * 0.5, MARGIN)
+	var frac := clampf(float(b["hp"]) / float(client.boss_def.max_hp), 0.0, 1.0)
+	_canvas.draw_rect(Rect2(pos, Vector2(w, BAR_H)), Color(0.12, 0.08, 0.1))
+	_canvas.draw_rect(Rect2(pos, Vector2(w * frac, BAR_H)), Color(0.95, 0.35, 0.45))
+	var phase_index := int(b["phase"])
+	var phase_name := ""
+	if phase_index < client.boss_def.phases.size():
+		phase_name = client.boss_def.phases[phase_index].name
+	_canvas.draw_string(ThemeDB.fallback_font, pos + Vector2(0.0, -6.0),
+		"%s   --   %s" % [client.boss_def.display_name, phase_name],
+		HORIZONTAL_ALIGNMENT_LEFT, -1, 14, Color(1.0, 0.75, 0.8))
+
+
+func _bar(pos: Vector2, frac: float, fill: Color, back: Color) -> void:
+	_canvas.draw_rect(Rect2(pos, Vector2(BAR_W, BAR_H)), back)
+	_canvas.draw_rect(Rect2(pos, Vector2(BAR_W * clampf(frac, 0.0, 1.0), BAR_H)), fill)
+
+
+func flash_hit() -> void:
+	_hit_flash = 1.0