feat: enhance Goldenrod Game Corner graphics extraction

Added functions to write raw graphics assets for the Slot Machine and Card Flip games, ensuring that the necessary files are generated when the corresponding symbols are present in the ROM. Updated the manifest to include required symbols for these assets, preventing fallback to labelled cells when graphics are missing.

src/import/RomImporter.lua

@@ -140,6 +140,12 @@ local VERSION_REQUIRED_FILES_OVERRIDE = {
     -- before the four ball tiles were extracted (#1502).
     "assets/generated/battle/hud/balls.png",
     "assets/generated/audio/programs.bin",
+    -- Goldenrod Game Corner reel + board art (#1581).  menu_gfx.lua used to
+    -- advertise these paths even when Slots*LZ / CardFlip* were absent from
+    -- the manifest, so a cache that never wrote the PNGs still looked
+    -- complete and SlotMachine crashed on its labelled-cell fallback.
+    "assets/generated/slots/gold_slots_1.png",
+    "assets/generated/card_flip/card_flip_1.png",
   },
 }
 -- Same Gen 2 extract, so a Silver cache is complete when the same files exist.