feat(sites): strata on the Banc du Vigilant drop-off and multi-scale seabed relief

Strata now take a world rectangle, so the 4 m ledges cover the whole break
and talus south of z = 118 m without touching la Saignée or the landmarks.
Roughness gains octave and fractal-type parameters; a SlopeRoughness
modifier roughens rock faces only. Both sites are re-baked with hummocks
from 250 m down to 5 m. The secondary item, the first debris piece and one
safe-route waypoint move a few metres to keep their contracts.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tests/unit/run_site_baker_tests.gd

@@ -8,7 +8,7 @@ const SiteTerrainData = preload("res://game/domain/sites/site_terrain_data.gd")
 
 const ZONE1_TERRAIN_PATH := "res://content/sites/zone1_vigilant_terrain.res"
 
-const TEST_COUNT := 44
+const TEST_COUNT := 48
 
 var _failures: Array[String] = []
 
@@ -23,6 +23,7 @@ func _init() -> void:
 	_test_outcrop()
 	_test_boulder_field()
 	_test_strata()
+	_test_slope_roughness()
 
 	if _failures.is_empty():
 		print("Site baker unit tests: %d passed, 0 failed." % TEST_COUNT)
@@ -187,7 +188,7 @@ func _test_strata() -> void:
 	recipe.origin_z_m = -10.0
 	recipe.primitives.append(SiteTerrainBaker.SlopedPlane.new(30.0, 1.0, 0.0, 0.0, 0.0))
 	var plain := SiteTerrainBaker.bake(recipe)
-	recipe.modifiers.append(SiteTerrainBaker.Strata.new(2.0, 0.9, 20.0, 35.0, Vector2.ZERO, 0.0))
+	recipe.modifiers.append(SiteTerrainBaker.Strata.new(2.0, 0.9, 20.0, 35.0, Rect2()))
 	var terraced := SiteTerrainBaker.bake(recipe)
 	var flat_cells := 0
 	var riser_cells := 0
@@ -202,17 +203,48 @@ func _test_strata() -> void:
 
 	var flat := _small_recipe()
 	flat.primitives.append(SiteTerrainBaker.SlopedPlane.new(30.3, 0.0, 0.0, 0.0, 0.0))
-	flat.modifiers.append(SiteTerrainBaker.Strata.new(2.0, 0.9, 20.0, 35.0, Vector2.ZERO, 0.0))
+	flat.modifiers.append(SiteTerrainBaker.Strata.new(2.0, 0.9, 20.0, 35.0, Rect2()))
 	var flat_data := SiteTerrainBaker.bake(flat)
 	_expect(is_equal_approx(flat_data.elevations_m[flat_data.index_of(10, 10)], -30.3), "strata leave flat ground alone")
 
 	var identity := _small_recipe()
 	identity.primitives.append(SiteTerrainBaker.SlopedPlane.new(30.0, 1.0, 0.0, 0.0, 0.0))
 	var before := SiteTerrainBaker.bake(identity)
-	identity.modifiers.append(SiteTerrainBaker.Strata.new(2.0, 0.0, 20.0, 35.0, Vector2.ZERO, 0.0))
+	identity.modifiers.append(SiteTerrainBaker.Strata.new(2.0, 0.0, 20.0, 35.0, Rect2()))
 	var after := SiteTerrainBaker.bake(identity)
 	_expect(before.elevations_m == after.elevations_m, "sharpness 0 is the identity")
 
+	# Depth 30.7 keeps the plane off the layer boundaries, where quantisation is the identity.
+	var banded := _small_recipe()
+	banded.primitives.append(SiteTerrainBaker.SlopedPlane.new(30.7, 1.0, 0.0, 0.0, 0.0))
+	var untouched := SiteTerrainBaker.bake(banded)
+	banded.modifiers.append(SiteTerrainBaker.Strata.new(2.0, 0.9, 20.0, 35.0, Rect2(-20.0, 0.0, 40.0, 20.0)))
+	var half := SiteTerrainBaker.bake(banded)
+	var north_same := half.elevations_m[half.index_of(13, 5)] == untouched.elevations_m[untouched.index_of(13, 5)]
+	var south_changed := half.elevations_m[half.index_of(13, 15)] != untouched.elevations_m[untouched.index_of(13, 15)]
+	_expect(north_same and south_changed, "strata stay inside their region")
+
+
+func _test_slope_roughness() -> void:
+	var recipe := _small_recipe()
+	recipe.primitives.append(SiteTerrainBaker.SlopedPlane.new(30.0, 0.0, 0.0, 0.0, 0.0))
+	recipe.primitives.append(SiteTerrainBaker.Blob.new(Vector2(10.0, 10.0), 5.0, 5.0, 12.0))
+	var smooth := SiteTerrainBaker.bake(recipe)
+	recipe.modifiers.append(SiteTerrainBaker.SlopeRoughness.new(5, 0.2, 1.0, 20.0, 40.0))
+	var rough := SiteTerrainBaker.bake(recipe)
+	_expect(rough.elevations_m[rough.index_of(0, 0)] == smooth.elevations_m[smooth.index_of(0, 0)], "slope roughness leaves flat sand untouched")
+	var flank_changed := false
+	for column in range(13, 18):
+		flank_changed = flank_changed or rough.elevations_m[rough.index_of(column, 15)] != smooth.elevations_m[smooth.index_of(column, 15)]
+	_expect(flank_changed, "slope roughness roughens the steep flank")
+	var octaves := _small_recipe()
+	octaves.primitives.append(SiteTerrainBaker.Roughness.new(7, 0.01, 2.0, 5, FastNoiseLite.FRACTAL_RIDGED))
+	var ridged := SiteTerrainBaker.bake(octaves)
+	var within := true
+	for elevation: float in ridged.elevations_m:
+		within = within and absf(elevation) <= 2.0 + 0.001
+	_expect(within, "roughness amplitude bounds the ridged multi-octave noise")
+
 
 func _test_zone1_artefact_is_stable() -> void:
 	var versioned := load(ZONE1_TERRAIN_PATH) as SiteTerrainData