feat(title): warm shader background, pulsing glow, drifting embers

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

client/scripts/ui/title/title_screen.gd

@@ -3,7 +3,9 @@ extends Control
 ## The entry-point screen (mock Title Screen). Editor-first (ADR 0001): the whole
 ## composition lives in TitleScreen.tscn; this script drives selection, input, and
 ## dispatches the menu. §2: presentation/state — no AI here (the DM enters at the
-## shell). The atmosphere (bg shader, glow, embers) is layered on in a later task.
+## shell). The atmosphere (warm bg shader, pulsing glow, drifting embers) is
+## configured in code from Palette (the DarkBay precedent) — see _apply_background,
+## _configure_embers, _pulse_glow.
 
 signal menu_activated(id: StringName)
 
@@ -15,6 +17,8 @@ var _sel: int = 0
 @onready var _menu: VBoxContainer = $Content/Menu
 @onready var _footer_left: Label = $FooterLeft
 @onready var _background: ColorRect = $Background
+@onready var _glow: ColorRect = $Glow
+@onready var _embers: GPUParticles2D = $Embers
 @onready var _rule: ColorRect = $Content/Rule
 
 
@@ -25,6 +29,10 @@ func _ready() -> void:
 
 	_background.color = Palette.STAGE_1
 	_rule.color = Palette.GOLD
+	_glow.color = Palette.BLOOD
+	_apply_background()
+	_configure_embers()
+	_pulse_glow()
 
 	_rows = []
 	for row in _menu.get_children():
@@ -42,6 +50,48 @@ func _fit_to_viewport() -> void:
 	size = get_viewport_rect().size
 
 
+func _apply_background() -> void:
+	# Palette-driven shader material set in code (the DarkBay precedent) so no hex
+	# lives in the shader/scene; the editor shows the ColorRect fallback.
+	var mat := ShaderMaterial.new()
+	mat.shader = load("res://assets/theme/shaders/title_background.gdshader")
+	mat.set_shader_parameter("warm", Palette.TITLE_WARM)
+	mat.set_shader_parameter("mid", Palette.TITLE_MID)
+	mat.set_shader_parameter("edge", Palette.STAGE_1)
+	_background.material = mat
+
+
+func _configure_embers() -> void:
+	var pm := ParticleProcessMaterial.new()
+	pm.emission_shape = ParticleProcessMaterial.EMISSION_SHAPE_BOX
+	pm.emission_box_extents = Vector3(760, 4, 0)  # a wide strip along the bottom
+	pm.direction = Vector3(0, -1, 0)
+	pm.spread = 12.0
+	pm.gravity = Vector3(0, -18, 0)
+	pm.initial_velocity_min = 24.0
+	pm.initial_velocity_max = 52.0
+	pm.scale_min = 0.4
+	pm.scale_max = 1.0
+	pm.color = Palette.GOLD_BRIGHT
+	# fade out over life
+	var ramp := Gradient.new()
+	ramp.set_color(0, Color(Palette.GOLD_BRIGHT, 0.0))
+	ramp.set_color(1, Color(Palette.GOLD_BRIGHT, 0.0))
+	ramp.add_point(0.15, Palette.GOLD_BRIGHT)
+	var tex := GradientTexture1D.new()
+	tex.gradient = ramp
+	pm.color_ramp = tex
+	_embers.process_material = pm
+
+
+func _pulse_glow() -> void:
+	# A slow warm pulse (the off-screen fire). A code tween, not an AnimationPlayer:
+	# a 2-keyframe modulate loop is trivial in code and motion is runtime-only anyway.
+	var tween := create_tween().set_loops().set_trans(Tween.TRANS_SINE)
+	tween.tween_property(_glow, "modulate:a", 0.8, 3.0)
+	tween.tween_property(_glow, "modulate:a", 0.5, 3.0)
+
+
 func _wire_row_mouse() -> void:
 	for i in range(_rows.size()):
 		var idx := i  # fresh per-iteration binding for the closures