perf(sites): validate the site once and hand collision the field array

DiveSite.configure() builds the height field once (TerrainHeightField
validates the data) instead of running the definition validation and
then the field construction again; the composition root relies on the
error returned by configure(). The collision shape takes the field's
row-major elevations directly instead of copying 263k cells one by one.

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

game/composition/vertical_slice/vertical_slice_root.gd

@@ -130,10 +130,6 @@ func _start_dive() -> void:
 	if definition == null:
 		push_error("dive site definition %s cannot be loaded" % _selected_site_path)
 		return
-	var definition_error := definition.validation_error()
-	if not definition_error.is_empty():
-		push_error("dive site %s is invalid: %s" % [_selected_site_path, definition_error])
-		return
 	var world_scene := load(DIVE_WORLD_SCENE_PATH) as PackedScene
 	if world_scene == null:
 		return

game/domain/sites/terrain_height_field.gd

@@ -59,6 +59,11 @@ func maximum_elevation_m() -> float:
 	return _maximum_elevation_m
 
 
+## Row-major elevations (index = row * columns + column), the HeightMapShape3D layout.
+func elevations_m() -> PackedFloat32Array:
+	return _data.elevations_m
+
+
 func elevation_at_cell(column: int, row: int) -> float:
 	return _data.elevations_m[_data.index_of(_clamp_column(column), _clamp_row(row))]
 

game/world/sites/bathymetric_terrain_actor.gd

@@ -116,12 +116,7 @@ func _build_collision() -> void:
 	var shape := HeightMapShape3D.new()
 	shape.map_width = _field.columns()
 	shape.map_depth = _field.rows()
-	var heights := PackedFloat32Array()
-	heights.resize(_field.columns() * _field.rows())
-	for row in _field.rows():
-		for column in _field.columns():
-			heights[row * _field.columns() + column] = _field.elevation_at_cell(column, row)
-	shape.map_data = heights
+	shape.map_data = _field.elevations_m()
 	_collision = CollisionShape3D.new()
 	_collision.name = "Collision"
 	_collision.shape = shape

game/world/sites/dive_site.gd

@@ -21,10 +21,10 @@ var _placeholder_count := 0
 func configure(definition: DiveSiteDefinition) -> String:
 	if definition == null:
 		return "dive site definition is missing"
-	var error := definition.validation_error()
-	if not error.is_empty():
-		return error
-	var terrain_error := _terrain.configure(definition.height_field())
+	var field := definition.height_field()
+	if field == null:
+		return "dive site definition is invalid"
+	var terrain_error := _terrain.configure(field)
 	if not terrain_error.is_empty():
 		return terrain_error
 	_definition = definition

tests/unit/run_site_domain_tests.gd

@@ -7,7 +7,7 @@ const SitePlacement = preload("res://game/domain/sites/site_placement.gd")
 const SiteRoute = preload("res://game/domain/sites/site_route.gd")
 const DiveSiteDefinition = preload("res://game/domain/sites/dive_site_definition.gd")
 
-const TEST_COUNT := 38
+const TEST_COUNT := 39
 
 var _failures: Array[String] = []
 
@@ -83,10 +83,12 @@ func _test_terrain_data_validation() -> void:
 
 
 func _test_height_field_sampling() -> void:
-	var field := TerrainHeightField.from_data(_make_terrain(3, 4))
+	var data := _make_terrain(3, 4)
+	var field := TerrainHeightField.from_data(data)
 	_expect(field != null, "valid data yields a field")
 	if field == null:
 		return
+	_expect(field.elevations_m() == data.elevations_m, "elevations are exposed in row-major data order")
 	_expect(field.bounds_m().is_equal_approx(Rect2(-10.0, 100.0, 4.0, 6.0)), "bounds cover (columns-1) by (rows-1) cells")
 	_expect(field.cell_world_position(2, 3).is_equal_approx(Vector3(-6.0, -26.0, 106.0)), "cell position follows origin and cell size")
 	_expect(is_equal_approx(field.elevation_at(-10.0, 100.0), -20.0), "elevation at a vertex is exact")