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/game/materials.gd

@@ -152,9 +152,24 @@ static func window_pane() -> StandardMaterial3D:
 	mat.emission_energy_multiplier = 0.0
 	return mat
 
+## Godot 4.7 changed the Compatibility light falloff in practice: the same
+## attenuation/range that read well on 4.3 leaves the night scene nearly black.
+## Use this switch for local lights until the project moves its baseline to 4.7.
+static func modern_light_falloff() -> bool:
+	var info := Engine.get_version_info()
+	return int(info.get("major", 4)) > 4 \
+		or (int(info.get("major", 4)) == 4 and int(info.get("minor", 0)) >= 7)
+
+## True only when a real RenderingDevice exists. The Compatibility renderer and
+## the headless dummy renderer return null, so the desktop-only effects can be
+## gated without Web/CI builds ever enabling them.
+static func forward_plus_active() -> bool:
+	return RenderingServer.get_rendering_device() != null
+
 ## Environment look shared by every phase: ACES tonemapping, soft glow, aerial
 ## fog for depth, and a mild contrast/saturation lift. Phase values come from
-## `GameManager.PHASE_LIGHTING`.
+## `GameManager.PHASE_LIGHTING`. Volumetric fog and SDFGI are only enabled when
+## Forward+ is actually available (the optional desktop preset).
 static func configure_environment(env: Environment, cfg: Dictionary) -> void:
 	if env == null:
 		return
@@ -180,6 +195,24 @@ static func configure_environment(env: Environment, cfg: Dictionary) -> void:
 	env.fog_density = float(cfg.get("fog_density", 0.0035))
 	env.fog_aerial_perspective = 0.25
 	env.fog_sky_affect = 0.4
+	var advanced := forward_plus_active()
+	env.volumetric_fog_enabled = advanced
+	env.sdfgi_enabled = advanced
+	if advanced:
+		# Desktop HQ: a shallow, cool fog gives the torch a visible shaft while
+		# keeping the entrance facade readable. Phase values are tuned per phase.
+		env.volumetric_fog_density = float(cfg.get("volumetric_density", 0.012))
+		env.volumetric_fog_albedo = cfg.get("volumetric_albedo", Color(0.55, 0.62, 0.72))
+		env.volumetric_fog_emission = cfg.get("volumetric_emission", Color.BLACK)
+		env.volumetric_fog_emission_energy = float(cfg.get("volumetric_energy", 0.0))
+		env.volumetric_fog_anisotropy = 0.25
+		env.volumetric_fog_length = 48.0
+		env.volumetric_fog_ambient_inject = 0.15
+		env.volumetric_fog_sky_affect = 0.2
+		env.sdfgi_use_occlusion = true
+		env.sdfgi_cascades = 4
+		env.sdfgi_min_cell_size = 0.2
+		env.sdfgi_energy = 0.7
 	env.adjustment_enabled = true
 	env.adjustment_brightness = 1.0
 	env.adjustment_contrast = float(cfg.get("contrast", 1.06))