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>

tests/integration/run_vertical_slice_foundation.gd

@@ -30,7 +30,7 @@ const ProductionInputAdapter = preload(
 	"res://game/infrastructure/input/production_input_adapter.gd"
 )
 
-const TEST_COUNT := 91
+const TEST_COUNT := 94
 
 var _failures: Array[String] = []
 
@@ -186,6 +186,9 @@ func _test_vehicle_slice(composition: VerticalSliceRoot) -> void:
 	_expect(detailing.practical_light_count() == 2, "cockpit uses two caged practical lights")
 	_expect(pressure_bulkhead.panel_count() == 1, "porthole bulkhead uses one continuous curved shell")
 	_expect(pressure_bulkhead.rectangular_whitebox_is_hidden(), "porthole rectangular whitebox is hidden")
+	_expect(pressure_bulkhead.glass_is_on_dedicated_layer(), "porthole glass sits alone on its render layer")
+	_expect(pressure_bulkhead.glass_roughness() >= 0.4, "porthole glass is rough enough to smear lamp reflections")
+	_expect(detailing.fill_light_ignores_porthole_glass(), "porthole fill light does not reflect in the glass")
 	_expect(analog_gauges.gauge_count() == 4, "dashboard exposes four primary analog instruments")
 	_expect(alert_box.indicator_count() == 3, "alert box exposes three pilot lights")
 	_expect(alert_box.active_indicator_count() == 1, "exactly one pilot light reflects the alert state")