fix(hud): have game mode hand HUD its target ship instead of group lookup

HUDController found its ship via get_first_node_in_group("ship"), a group
that has 2+ members once a match has an AI opponent — it only worked
because the player ship happened to spawn first. spawn_camera_rig now
wires the HUD's ship the same way it already wires the camera rig's
target.

Game/scripts/HUDController.gd

@@ -1,7 +1,9 @@
-# HUD Controller - discovers the ship/camera/game mode via groups and routes
-# their signals to the display widgets. All flight data is rendered by
-# aircraft-style instruments (attitude indicator, heading tape, bar gauges) —
-# this node is only the wiring hub; the instruments are dumb displays.
+# HUD Controller - receives its target ship from the game mode (see
+# GameMode.spawn_camera_rig), discovers the camera rig/game mode via groups,
+# and routes their signals to the display widgets. All flight data is
+# rendered by aircraft-style instruments (attitude indicator, heading tape,
+# bar gauges) — this node is only the wiring hub; the instruments are dumb
+# displays.
 extends CanvasLayer
 class_name HUDController
 
@@ -33,10 +35,11 @@ func _ready():
 	_initialize_hud()
 
 func _initialize_hud():
-	# Find the ship
-	ship = get_tree().get_first_node_in_group("ship")
+	# `ship` is assigned by the game mode (GameMode.spawn_camera_rig) before
+	# this runs — not discovered via group, since the "ship" group can have
+	# 2+ members and there's no reliable way to tell which one is "ours".
 	if not ship:
-		push_error("HUDController: No ship found in 'ship' group")
+		push_error("HUDController: No ship assigned")
 		return
 
 	print("HUDController: Found ship: ", ship.name)