feat: surfing minigame overhaul + authentic Game Corner rendering

Surfing minigame:
- Add title screen (ROUTINE_TITLE) with Pikachu intro, logo banner, instructions
- Add GLSL HBlank wave distortion shader, OAM water spray/splash sprites
- Add multi-path asset loader, isMinigame/isFixedSpeed flags, crash recovery fixes
- Extract SurfingPikachu graphics + composite title_bg.png from ROM

Game Corner (built visual layer from ROM assets; logic existed, rendering was placeholder):
- SlotMachine: GBC tilemap background, authentic reel symbol sprites, Golem/Chansey
  near-miss animations, lit/unlit lights, payout panel
- CardFlip: GBC tilemap board, hardware-accurate card flip sequence, OAM cursor frame
- RomExtractorGen2: extract slots + card_flip sprite sheets and tilemaps

Tests: SurfingMinigame units 8-13; 500-spin SlotMachine and 500-hand CardFlip stress tests

src/import/RomExtractorGen2.lua

@@ -5136,6 +5136,82 @@ function RomExtractorGen2:extractMenuGfx()
   end
   if eggHatch.egg or eggHatch.shell then out.eggHatch = eggHatch end
 
+  -- Goldenrod Game Corner: Slot Machine graphics assets
+  if self.symbols["Slots1LZ"] then
+    local raw1 = self:decompressLz3Symbol("Slots1LZ")
+    self:write2bpp(raw1, 16, #raw1 / 4, "slots/gold_slots_1.png")
+  end
+  if self.symbols["Slots2LZ"] then
+    local raw2 = self:decompressLz3Symbol("Slots2LZ")
+    -- In Pokemon Gold ROM, Seven symbol (first 4 tiles = 64 bytes) has inverted bit polarity
+    for i = 1, math.min(64, #raw2) do
+      raw2[i] = bit.band(bit.bnot(raw2[i]), 0xFF)
+    end
+    self:write2bpp(raw2, 16, #raw2 / 4, "slots/gold_slots_2.png")
+  end
+  if self.symbols["Slots3LZ"] then
+    local raw3 = self:decompressLz3Symbol("Slots3LZ")
+    self:write2bpp(raw3, 24, #raw3 / 6, "slots/gold_slots_3.png", true)
+    -- Slots3LZ is a 24px-wide (3 tiles), 240px-tall (30 tiles) sprite sheet containing:
+    --   Y=0:   Golem 1 (Standing, 24x32)
+    --   Y=32:  Golem 2 (Ball, 24x32)
+    --   Y=64:  Chansey 1 (Standing / Step 1, 24x32)
+    --   Y=96:  Chansey 2 (Step 2, 24x32)
+    --   Y=128: Chansey 3 (Step 3, 24x32)
+    --   Y=160: Chansey 4 (Arm raised / Step 4, 24x32)
+    --   Y=192: Chansey 5 (Egg Drop pose, 24x32)
+    --   Y=224: Egg (8x16 at X=0)
+    self:write2bpp(raw3, 24, #raw3 / 6, "slots/gold_slots_actors.png", true)
+  end
+  if self.symbols["SlotsTilemap"] then
+    local symbol = self:symbol("SlotsTilemap")
+    local tm = self.rom:bytes(symbol.bank, symbol.address, 20 * 12)
+    self:save(tm, "slots/gold_slots.tilemap")
+  end
+
+  -- Goldenrod Game Corner: Card Flip graphics assets
+  if self.symbols["CardFlipLZ01"] then
+    local raw1 = self:decompressLz3Symbol("CardFlipLZ01")
+    self:write2bpp(raw1, 128, #raw1 / 32, "card_flip/card_flip_1.png")
+  end
+  if self.symbols["CardFlipLZ02"] then
+    local raw2 = self:decompressLz3Symbol("CardFlipLZ02")
+    self:write2bpp(raw2, 24, #raw2 / 6, "card_flip/card_flip_2.png")
+  end
+  if self.symbols["CardFlipLZ03"] then
+    local raw3 = self:decompressLz3Symbol("CardFlipLZ03")
+    self:write2bpp(raw3, 8, #raw3 / 2, "card_flip/card_flip_3.png")
+  end
+  if self.symbols["CardFlipOnButtonGFX"] then
+    local symbol = self:symbol("CardFlipOnButtonGFX")
+    self:write2bpp(self.rom:bytes(symbol.bank, symbol.address, 16), 8, 8, "card_flip/on.png")
+  end
+  if self.symbols["CardFlipOffButtonGFX"] then
+    local symbol = self:symbol("CardFlipOffButtonGFX")
+    self:write2bpp(self.rom:bytes(symbol.bank, symbol.address, 16), 8, 8, "card_flip/off.png")
+  end
+  if self.symbols["CardFlipTilemap"] then
+    local symbol = self:symbol("CardFlipTilemap")
+    local tm = self.rom:bytes(symbol.bank, symbol.address, 11 * 12)
+    self:save(tm, "card_flip/card_flip.tilemap")
+  end
+
+  out.slots = {
+    sheet1 = "assets/generated/slots/gold_slots_1.png",
+    sheet2 = "assets/generated/slots/gold_slots_2.png",
+    sheet3 = "assets/generated/slots/gold_slots_3.png",
+    tilemap = "assets/generated/slots/gold_slots.tilemap",
+  }
+
+  out.cardFlip = {
+    sheet1 = "assets/generated/card_flip/card_flip_1.png",
+    sheet2 = "assets/generated/card_flip/card_flip_2.png",
+    sheet3 = "assets/generated/card_flip/card_flip_3.png",
+    on = "assets/generated/card_flip/on.png",
+    off = "assets/generated/card_flip/off.png",
+    tilemap = "assets/generated/card_flip/card_flip.tilemap",
+  }
+
   self:write("menu_gfx", out)
   self:tick("Menu graphics", 1, 1)
   return out