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

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

client/scenes/title/TitleScreen.tscn

@@ -18,6 +18,21 @@ anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
 
+[node name="Glow" type="ColorRect" parent="."]
+layout_mode = 1
+anchors_preset = 12
+anchor_top = 1.0
+anchor_right = 1.0
+anchor_bottom = 1.0
+offset_top = -420.0
+mouse_filter = 2
+
+[node name="Embers" type="GPUParticles2D" parent="."]
+position = Vector2(960, 1080)
+amount = 24
+lifetime = 9.0
+preprocess = 4.0
+
 [node name="KeyArt" type="Label" parent="."]
 layout_mode = 1
 anchors_preset = 6