Add tentacled boss planet encounter

tests/_boss_planet_preview.gd

@@ -0,0 +1,49 @@
+extends Node2D
+
+# Stable portrait composition for visually checking #188. The real surface,
+# encounter, fleet, UI, minions, open eyes and laser telegraph are all used;
+# only their timers are frozen once the representative second phase is laid
+# out so a screenshot does not depend on capture timing.
+
+var surface: Node
+var laid_out: bool = false
+
+
+func _ready() -> void:
+	GameState.reset_new_game()
+	GameState.intro_active = false
+	GameState.reset_quests(false)
+	GameState.planet_name = "Many-Eyed Deep"
+	GameState.planet_id = "preview:boss"
+	GameState.planet_definition_id = "boss"
+	GameState.surviving_ship_count = 3
+	GameState.surviving_vessel_types = PackedStringArray([
+		GameState.VESSEL_INTERCEPTOR,
+		GameState.VESSEL_GAS_BOMBER,
+		GameState.VESSEL_LASER,
+	])
+	surface = load("res://surface/PlanetSurface.tscn").instantiate()
+	add_child(surface)
+	surface.get_node("FadeOverlay/FadeRect").visible = false
+
+
+func _process(_delta: float) -> void:
+	if laid_out:
+		return
+	laid_out = true
+	var encounter: Node = surface.get_node("SurfaceFeatures/BossEncounter")
+	var boss: Node2D = encounter.get_node("Boss")
+	boss.wave_timer = 999.0
+	boss.laser_timer = 999.0
+	boss.phase = boss.Phase.LASER_STORM
+	for i in range(3):
+		boss.eyes[i].open_eye()
+		boss.eyes_opened += 1
+	boss.spawn_wave()
+	for minion in get_tree().get_nodes_in_group("boss_minions"):
+		minion.speed = 0.0
+		minion.acceleration = 0.0
+	boss.laser_charge_time = 999.0
+	boss.fire_laser_volley()
+	encounter._process(0.0)
+	get_tree().paused = true