Add serial upload tool for rapid Lua game iteration

Implements a complete serial upload workflow that allows uploading and
immediately testing Lua games via USB serial connection.

New Components:
- SerialUploader: Receives files via serial, writes to SD card
- upload_game.py: Python tool for sending files from host computer
- Protocol: Text-based with base64 encoding for reliability

Key Features:
- Uploads file to /games folder on SD card
- Overwrites existing files (FA_CREATE_ALWAYS)
- Auto-launches uploaded game immediately
- Proper memory cleanup (prevents Lua state conflicts)

SD Card Fixes:
- Fixed SPI speed management (12.5MHz for SD, 32MHz for display)
- Fixed SD write protocol (poll for data response token)
- Added speed switching wrappers around all FatFS operations
- Cleaned up excessive debug output

Game Launcher Improvements:
- Added clear_games() to prevent duplicate registrations
- Added cleanup in select_game_by_name() to delete old instances
- Added exact match priority in game selection
- LuaGameLoader now has clear_factory_data() for memory cleanup

Integration:
- Added serial_uploader to CMakeLists.txt
- Integrated into main loop in basic1.cpp
- Re-scans games after upload to pick up new files

Documentation:
- UPLOAD_TOOL.md: Usage instructions
- sd_card_best_practices.md: Critical lessons learned

Known Issues:
- Game launch after upload occasionally causes freeze (needs investigation)
- Display may not refresh properly after upload

Usage:
  python upload_game.py games/lua_examples/2048.lua /dev/tty.usbmodem101

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

lib/game_launcher.h

@@ -78,13 +78,25 @@ public:
      * @brief Reset launcher to show menu again
      */
     void reset();
-    
+
+    /**
+     * @brief Clear all registered games (useful before re-scanning)
+     */
+    void clear_games();
+
     /**
      * @brief Check if a game is currently selected
      * @return true if game selected, false if in menu
      */
     bool is_game_selected() const { return selected_game != nullptr; }
 
+    /**
+     * @brief Select a game by name (for programmatic launching)
+     * @param name Game name to select (partial match supported)
+     * @return true if game was found and launched, false otherwise
+     */
+    bool select_game_by_name(const char* name);
+
 private:
     uint16_t width;
     uint16_t height;