Add sunlit shallows site with localized sun shafts

New visual test site under game/world/sites: flat sandy floor at
-40 m, calm surface at 0 m, fixed daytime sun ahead of and above
the submarine. Light shafts come from a shadow-only surface
occluder whose alpha-scissor ripples open only inside a pool a few
tens of metres ahead; a subtractive FogVolume cancels the global
volumetric fog above the water, and an unshaded ceiling mesh shows
the lit underside of the surface inside that pool. A composed
world (sunlit_shallows_world.tscn) mounts the submarine, cockpit
and camera rig in it, with the projectors kept out of the fog.

Cockpit: the porthole glass moves to its own render layer with a
rougher material and the porthole fill light excludes that layer,
so interior lamps no longer mirror as hard specular points.

Quality gate: new integration suite for the site (42 checks), three
glass assertions in the foundation suite, and the Input-access
architecture rule now matches both path separators so the gate runs
on Windows. project.godot raises the volumetric fog froxel grid to
128 so the shafts stay readable.

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

game/world/sites/sunlit_shallows_environment.gd

@@ -0,0 +1,161 @@
+class_name SunlitShallowsEnvironment
+extends Node3D
+
+## Visual test site: flat floor, calm water, fixed daytime sun.
+## The hour never changes, so the sun transform is a constant and the only
+## motion is the slow ripple drift inside the two shaders.
+
+const SURFACE_LEVEL_M := 0.0
+const FLOOR_DEPTH_M := -40.0
+## Air above the calm surface holds no scattering medium: a subtractive
+## FogVolume cancels the global volumetric fog there so the view never shows
+## an unshadowed glow above the water.
+const AIR_VOLUME_HEIGHT_M := 80.0
+const VOLUMETRIC_FOG_DENSITY := 0.035
+const SITE_EXTENT_M := 240.0
+## Sun sits ahead of the observer (world -Z) and high: shafts travel down
+## toward the submarine, as in the cockpit visual target.
+const SUN_ROTATION_DEGREES := Vector3(-44.0, 162.0, 0.0)
+const NOISE_SEED := 7
+## Calm water: ripple drift stays well under 0.05 texture units per second.
+const SURFACE_DRIFT_SPEED := 0.012
+## Sunlight only breaks through a pool of surface a few tens of metres ahead of
+## the submarine (world -Z), so the shafts land in front of the porthole.
+const SHAFT_POOL_CENTER_XZ_M := Vector2(-14.0, -31.0)
+const SHAFT_POOL_RADIUS_M := 22.0
+const SHAFT_POOL_EDGE_M := 12.0
+## Coarser ripples give a few broken oblique shafts rather than a dense fan.
+const SURFACE_RIPPLE_SCALE := 0.025
+## The underside of the surface is drawn dark, lit only inside the pool.
+const SURFACE_CEILING_LIT_SCALE := 0.3
+
+const SURFACE_OCCLUDER_SHADER := preload(
+	"res://game/world/sites/sunlit_shallows_surface_occluder.gdshader"
+)
+const CAUSTIC_FLOOR_SHADER := preload(
+	"res://game/world/sites/sunlit_shallows_caustic_floor.gdshader"
+)
+const SURFACE_CEILING_SHADER := preload(
+	"res://game/world/sites/sunlit_shallows_surface_ceiling.gdshader"
+)
+
+
+func _ready() -> void:
+	_fix_sun()
+	_add_flat_floor()
+	_add_surface_occluder()
+	_add_surface_ceiling()
+	_add_air_fog_cut()
+
+
+func _fix_sun() -> void:
+	var sun := get_node_or_null("Sun") as DirectionalLight3D
+	if sun == null:
+		return
+	sun.rotation_degrees = SUN_ROTATION_DEGREES
+
+
+func _add_flat_floor() -> void:
+	var plane := PlaneMesh.new()
+	plane.size = Vector2(SITE_EXTENT_M, SITE_EXTENT_M)
+	plane.subdivide_width = 1
+	plane.subdivide_depth = 1
+
+	var material := ShaderMaterial.new()
+	material.shader = CAUSTIC_FLOOR_SHADER
+	material.set_shader_parameter("caustic_noise", _make_ripple_noise(0.007))
+
+	var body := StaticBody3D.new()
+	body.name = "FlatFloor"
+	body.position = Vector3(0.0, FLOOR_DEPTH_M, 0.0)
+	body.set_meta("sonar_material", 1)
+	body.set_meta("sonar_reflectivity", 0.6)
+
+	var mesh_instance := MeshInstance3D.new()
+	mesh_instance.name = "Mesh"
+	mesh_instance.mesh = plane
+	mesh_instance.material_override = material
+	body.add_child(mesh_instance)
+
+	var collision := CollisionShape3D.new()
+	collision.name = "Collision"
+	var shape := BoxShape3D.new()
+	shape.size = Vector3(SITE_EXTENT_M, 1.0, SITE_EXTENT_M)
+	collision.shape = shape
+	collision.position = Vector3(0.0, -0.5, 0.0)
+	body.add_child(collision)
+	add_child(body)
+
+
+func _add_surface_occluder() -> void:
+	var plane := PlaneMesh.new()
+	plane.size = Vector2(SITE_EXTENT_M, SITE_EXTENT_M)
+
+	var material := ShaderMaterial.new()
+	material.shader = SURFACE_OCCLUDER_SHADER
+	material.set_shader_parameter("ripple_noise", _make_ripple_noise(0.009))
+	material.set_shader_parameter("drift_speed", SURFACE_DRIFT_SPEED)
+	material.set_shader_parameter("ripple_scale", SURFACE_RIPPLE_SCALE)
+	material.set_shader_parameter("pool_center_xz", SHAFT_POOL_CENTER_XZ_M)
+	material.set_shader_parameter("pool_radius", SHAFT_POOL_RADIUS_M)
+	material.set_shader_parameter("pool_edge", SHAFT_POOL_EDGE_M)
+
+	var occluder := MeshInstance3D.new()
+	occluder.name = "CalmSurfaceOccluder"
+	occluder.position = Vector3(0.0, SURFACE_LEVEL_M, 0.0)
+	occluder.mesh = plane
+	occluder.material_override = material
+	occluder.cast_shadow = GeometryInstance3D.SHADOW_CASTING_SETTING_SHADOWS_ONLY
+	add_child(occluder)
+
+
+func _add_surface_ceiling() -> void:
+	var plane := PlaneMesh.new()
+	plane.size = Vector2(SITE_EXTENT_M * 1.5, SITE_EXTENT_M * 1.5)
+
+	var material := ShaderMaterial.new()
+	material.shader = SURFACE_CEILING_SHADER
+	material.set_shader_parameter("ripple_noise", _make_ripple_noise(0.009))
+	material.set_shader_parameter("drift_speed", SURFACE_DRIFT_SPEED)
+	material.set_shader_parameter("pool_center_xz", SHAFT_POOL_CENTER_XZ_M)
+	material.set_shader_parameter("pool_radius", SHAFT_POOL_RADIUS_M)
+	material.set_shader_parameter("lit_scale", SURFACE_CEILING_LIT_SCALE)
+
+	var ceiling := MeshInstance3D.new()
+	ceiling.name = "SurfaceCeiling"
+	ceiling.position = Vector3(0.0, SURFACE_LEVEL_M, 0.0)
+	ceiling.mesh = plane
+	ceiling.material_override = material
+	ceiling.cast_shadow = GeometryInstance3D.SHADOW_CASTING_SETTING_OFF
+	add_child(ceiling)
+
+
+func _add_air_fog_cut() -> void:
+	var air := FogVolume.new()
+	air.name = "AirFogCut"
+	air.shape = RenderingServer.FOG_VOLUME_SHAPE_BOX
+	air.size = Vector3(SITE_EXTENT_M * 1.5, AIR_VOLUME_HEIGHT_M, SITE_EXTENT_M * 1.5)
+	air.position = Vector3(0.0, SURFACE_LEVEL_M + AIR_VOLUME_HEIGHT_M * 0.5, 0.0)
+	var material := FogMaterial.new()
+	material.density = -VOLUMETRIC_FOG_DENSITY
+	material.edge_fade = 0.0
+	air.material = material
+	add_child(air)
+
+
+func _make_ripple_noise(frequency: float) -> NoiseTexture2D:
+	var noise := FastNoiseLite.new()
+	noise.seed = NOISE_SEED
+	noise.noise_type = FastNoiseLite.TYPE_SIMPLEX_SMOOTH
+	noise.frequency = frequency
+	noise.fractal_octaves = 3
+	noise.fractal_lacunarity = 2.1
+	noise.fractal_gain = 0.45
+
+	var texture := NoiseTexture2D.new()
+	texture.width = 512
+	texture.height = 512
+	texture.seamless = true
+	texture.generate_mipmaps = true
+	texture.noise = noise
+	return texture