Add the optional Forward+ desktop HQ build

Package a Forward+ preset with volumetric fog, SDFGI and a volumetric flashlight
for a separate Linux/Windows Desktop HQ zip. Gate the effects on a real
RenderingDevice, tune LATE fog, and adapt local light falloff for Godot 4.7.
Record the Compatibility/Forward+ A/B captures and metrics, add the artifact to
the build/publish scripts, and keep the default Compatibility/Web path
unchanged. Headless 231/231, Python 87/87; exported HQ binary boots with Vulkan.

src/test/tests/test_door_and_flashlight.gd

@@ -43,8 +43,11 @@ func test_flashlight_aims_a_tight_forward_spot() -> bool:
 	var c := TestUtils.check(lamp != null and lamp.spot_angle <= 20.0,
 		"flashlight cone is narrow enough to read as a torch")
 	var d := TestUtils.check(lamp != null and not lamp.visible, "flashlight starts off")
+	var e := TestUtils.check(lamp != null
+		and is_zero_approx(lamp.light_volumetric_fog_energy),
+		"headless/compatibility builds leave the flashlight non-volumetric")
 	root.free()
-	return a and b and c and d
+	return a and b and c and d and e
 
 func test_flashlight_widens_perception() -> bool:
 	## Without the flashlight, an NPC at AWARE_RADIUS + 3 m is unaware.