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/presentation/cockpit/cockpit_pressure_bulkhead.gd

@@ -4,6 +4,18 @@ extends Node3D
 ## Imported pressure hull (end cap, knuckle and barrel in one shell) and the
 ## porthole bolted into it. Both models are instanced by `cockpit_interior.tscn`.
 
+## The porthole glass lives alone on render layer 2 so interior lights that
+## sit right behind it (the cool porthole fill) can leave it out of their cull
+## mask instead of mirroring themselves as a hard specular point.
+const PORTHOLE_GLASS_RENDER_LAYER_BIT := 1 << 1
+## Imported glass is near-mirror smooth; a little roughness turns the remaining
+## lamp reflections into soft smears rather than pinpoints.
+const PORTHOLE_GLASS_ROUGHNESS := 0.45
+
+const CockpitMeshFactory = preload(
+	"res://game/presentation/cockpit/cockpit_mesh_factory.gd"
+)
+
 const WHITEBOX_NAMES: Array[String] = [
 	"LeftBulkhead",
 	"RightBulkhead",
@@ -26,6 +38,21 @@ func _ready() -> void:
 		push_error("Pressure hull or porthole model is missing a node")
 		return
 	_porthole_glass.cast_shadow = GeometryInstance3D.SHADOW_CASTING_SETTING_OFF
+	_porthole_glass.layers = PORTHOLE_GLASS_RENDER_LAYER_BIT
+	var glass_material := CockpitMeshFactory.own_surface_material(_porthole_glass)
+	if glass_material != null:
+		glass_material.roughness = PORTHOLE_GLASS_ROUGHNESS
+
+
+func glass_is_on_dedicated_layer() -> bool:
+	return _porthole_glass != null and _porthole_glass.layers == PORTHOLE_GLASS_RENDER_LAYER_BIT
+
+
+func glass_roughness() -> float:
+	if _porthole_glass == null:
+		return 0.0
+	var material := _porthole_glass.get_active_material(0) as BaseMaterial3D
+	return 0.0 if material == null else material.roughness
 
 
 func panel_count() -> int: