Use a vertical fade for the flashlight beam

A GradientTexture1D varies along U, so the cone showed a bright ring; build a
1×64 vertical ramp for UV.y instead (faint at the lens, brightest near the
start, gone before the tip). Regenerate the affected captures; headless 227/227,
compare 11 good / 0 bad.

src/game/materials.gd

@@ -139,13 +139,21 @@ static func light_beam() -> StandardMaterial3D:
 	mat.cull_mode = BaseMaterial3D.CULL_DISABLED
 	mat.depth_draw_mode = BaseMaterial3D.DEPTH_DRAW_DISABLED
 	mat.albedo_color = Color(1.0, 0.95, 0.82, 1.0)
-	var fade := Gradient.new()
-	fade.set_color(0, Color(1.0, 0.95, 0.82, 0.08))
-	fade.add_point(0.15, Color(1.0, 0.95, 0.82, 0.5))
-	fade.set_color(fade.get_point_count() - 1, Color(1.0, 0.95, 0.82, 0.0))
-	var ramp := GradientTexture1D.new()
-	ramp.gradient = fade
-	mat.albedo_texture = ramp
+	# A vertical ramp, not a GradientTexture1D: a cylinder's UV.y runs along its
+	# height, while the 1D gradient varies with U and would paint a bright ring.
+	var ramp := Image.create(1, 64, false, Image.FORMAT_RGBA8)
+	for y in 64:
+		var t := float(y) / 63.0
+		# Symmetric fade (bright in the middle, gone at both ends) so the look
+		# does not depend on which way CylinderMesh orients its V coordinate; the
+		# far end must never show as a bright ring.
+		var alpha := 0.0
+		if t < 0.5:
+			alpha = lerpf(0.0, 0.3, t / 0.5)
+		else:
+			alpha = lerpf(0.3, 0.0, (t - 0.5) / 0.5)
+		ramp.set_pixel(0, y, Color(1.0, 1.0, 1.0, alpha))
+	mat.albedo_texture = ImageTexture.create_from_image(ramp)
 	mat.texture_filter = BaseMaterial3D.TEXTURE_FILTER_LINEAR
 	return mat