Add Katakana, Korean and Thai games and difficulty levels

- decks package: Hiragana, Katakana, Hangul jamo and Thai consonants
  (Thai readings carry the letter's name word, since sounds repeat)
- Per-script fonts: Jua for Hangul, Mali for Thai (both OFL)
- Memory game works with any deck; Easy 3x4, Normal 4x6, Hard 4x8
- Language menus pick a deck and difficulty, with number/arrow key shortcuts
- Tests cover every deck, difficulty, and font glyph coverage

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

main.odin

@@ -4,6 +4,7 @@ import raylib "vendor:raylib"
 import assets "src/assets"
 import audio "src/audio"
 import card "src/card"
+import decks "src/decks"
 import memory "src/memory"
 import screens "src/screens"
 import themes "src/themes"
@@ -12,9 +13,9 @@ import ui "src/ui"
 // Where Escape takes you from each screen (nil = quit)
 parent_screen :: proc(screen: themes.Screen) -> Maybe(themes.Screen) {
     switch screen {
-    case .MAIN_MENU:       return nil
-    case .JAPANESE_MEMORY: return .JAPANESE_MENU
-    case .JAPANESE_MENU, .KOREAN_MENU, .THAI_MENU: return .MAIN_MENU
+    case .MAIN_MENU:     return nil
+    case .LANGUAGE_MENU: return .MAIN_MENU
+    case .MEMORY:        return .LANGUAGE_MENU
     }
     return nil
 }
@@ -40,6 +41,8 @@ main :: proc() {
     defer memory.unload()
 
     screen := themes.Screen.MAIN_MENU
+    language := decks.Language.JAPANESE
+    difficulty := memory.Difficulty.NORMAL
     running := true
     for running && !raylib.WindowShouldClose() {
         dt := raylib.GetFrameTime()
@@ -52,27 +55,37 @@ main :: proc() {
             }
         }
 
-        if screen == .JAPANESE_MEMORY {
+        if screen == .MEMORY {
             memory.update(dt)
         }
 
         raylib.BeginDrawing()
         ui.begin_frame()
         next := screen
+        start_deck: Maybe(decks.Deck_Id)
         switch screen {
-        case .MAIN_MENU:       next = screens.main_menu()
-        case .JAPANESE_MENU:   next = screens.japanese_menu()
-        case .JAPANESE_MEMORY: next = memory.draw()
-        case .KOREAN_MENU:     next = screens.korean_menu()
-        case .THAI_MENU:       next = screens.thai_menu()
+        case .MAIN_MENU:
+            if picked, ok := screens.main_menu().?; ok {
+                language = picked
+                next = .LANGUAGE_MENU
+            }
+        case .LANGUAGE_MENU:
+            switch result in screens.language_menu(language, &difficulty) {
+            case decks.Deck_Id:
+                start_deck = result
+                next = .MEMORY
+            case themes.Screen:
+                next = result
+            }
+        case .MEMORY:
+            next = memory.draw()
         }
         ui.end_frame()
         raylib.EndDrawing()
 
-        // Start a fresh game when entering the memory screen (outside of drawing,
-        // because building card faces renders into textures)
-        if next == .JAPANESE_MEMORY && screen != .JAPANESE_MEMORY {
-            memory.start(themes.JAPAN)
+        // Building card faces renders into textures, so do it outside of drawing
+        if deck, ok := start_deck.?; ok {
+            memory.start(deck, difficulty)
         }
         screen = next
     }