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

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

client/scripts/theme/palette.gd

@@ -19,6 +19,10 @@ const BORDER_3 := Color("4a4238")
 const BORDER_4 := Color("3a352e")
 const BORDER_5 := Color("1a1512")
 
+# --- Title-screen ambiance (warm radial background) ---
+const TITLE_WARM := Color("2a2018")   # radial centre
+const TITLE_MID := Color("160f0a")    # radial midpoint (STAGE_1 is the edge)
+
 # --- Parchment ---
 const SHEET_TOP := Color("ece2ca")
 const SHEET_BOTTOM := Color("e4d8bd")