feat(composition): dive world assembled from a selected site definition

The calibration site spawn sat 16 m from the south bounds edge, inside the
40 m warning margin. The vehicle_test recipe now extends the terrain and
playable bounds 42 m to the south so the spawn is inside the zone.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

tests/integration/run_vertical_slice_foundation.gd

@@ -5,6 +5,7 @@ const VerticalSliceRoot = preload(
 )
 const MainMenuScreen = preload("res://game/presentation/main_menu/main_menu_screen.gd")
 const CockpitHud = preload("res://game/presentation/cockpit/cockpit_hud.gd")
+const PlayableBoundsStatus = preload("res://game/application/sites/playable_bounds_status.gd")
 const CockpitDetailing = preload(
 	"res://game/presentation/cockpit/cockpit_detailing.gd"
 )
@@ -19,7 +20,7 @@ const ProductionInputAdapter = preload(
 	"res://game/infrastructure/input/production_input_adapter.gd"
 )
 
-const TEST_COUNT := 78
+const TEST_COUNT := 83
 
 var _failures: Array[String] = []
 
@@ -75,6 +76,7 @@ func _test_vehicle_slice(composition: VerticalSliceRoot) -> void:
 	var continue_button := menu.get_node("%ContinueButton") as Button
 	_expect(continue_button.disabled, "continue is disabled without save")
 	var new_game_button := menu.get_node("%NewGameButton") as Button
+	composition.select_dive_site("res://content/sites/vehicle_test.tres")
 	new_game_button.pressed.emit()
 	await process_frame
 	await physics_frame
@@ -110,6 +112,22 @@ func _test_vehicle_slice(composition: VerticalSliceRoot) -> void:
 	_expect(sonar_service != null, "production sonar service is assembled")
 	_expect(sonar_display != null, "shared sonar presentation is assembled")
 	_expect(composition.latest_update() != null, "dive session starts with a typed update")
+	_expect(composition.dive_site() != null, "composition instantiates the selected dive site")
+	_expect(
+		composition.dive_site() != null
+		and composition.dive_site().definition().site_id == &"vehicle_test",
+		"selected site definition drives the world"
+	)
+	_expect(
+		actor != null and actor.global_position.is_equal_approx(Vector3(0.0, -12.0, 12.0)),
+		"submarine spawns at the site spawn point"
+	)
+	_expect(
+		composition.latest_bounds_status() != null
+		and composition.latest_bounds_status().state == PlayableBoundsStatus.State.INSIDE,
+		"spawn is inside the playable bounds"
+	)
+	_expect(hud != null and not hud.bounds_warning_visible(), "no bounds warning inside the zone")
 	if (
 		actor == null
 		or camera == null