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>

upload_game.py

@@ -0,0 +1,149 @@
+#!/usr/bin/env python3
+"""
+Lua Game Uploader for RP2350
+Rapidly upload and execute Lua games via USB serial for quick iteration.
+
+Usage:
+    python upload_game.py <lua_file> [serial_port]
+
+Example:
+    python upload_game.py my_game.lua /dev/ttyACM0
+    python upload_game.py my_game.lua COM3
+"""
+
+import sys
+import os
+import base64
+import serial
+import time
+from pathlib import Path
+
+def find_serial_port():
+    """Auto-detect the RP2350 serial port"""
+    import serial.tools.list_ports
+
+    # Look for Pico/RP2350 devices
+    ports = list(serial.tools.list_ports.comports())
+    for port in ports:
+        # Common VID/PID for Raspberry Pi Pico
+        if 'Pico' in port.description or \
+           'RP2350' in port.description or \
+           'RP2040' in port.description or \
+           (port.vid == 0x2E8A):  # Raspberry Pi VID
+            return port.device
+
+    # Fallback: return first available port
+    if ports:
+        print(f"Warning: Could not find RP2350, using first available port: {ports[0].device}")
+        return ports[0].device
+
+    return None
+
+def upload_game(lua_file, serial_port=None):
+    """Upload a Lua game file to the RP2350 and execute it"""
+
+    # Check if file exists
+    if not os.path.exists(lua_file):
+        print(f"Error: File '{lua_file}' not found")
+        return False
+
+    # Read the file
+    with open(lua_file, 'rb') as f:
+        file_data = f.read()
+
+    file_size = len(file_data)
+    filename = os.path.basename(lua_file)
+
+    # Ensure filename has .lua extension
+    if not filename.endswith('.lua'):
+        filename += '.lua'
+
+    print(f"Uploading {filename} ({file_size} bytes)...")
+
+    # Auto-detect serial port if not provided
+    if serial_port is None:
+        serial_port = find_serial_port()
+        if serial_port is None:
+            print("Error: No serial port found. Please specify manually.")
+            return False
+        print(f"Using serial port: {serial_port}")
+
+    try:
+        # Open serial connection
+        ser = serial.Serial(serial_port, 115200, timeout=5)
+        time.sleep(0.1)  # Wait for connection to stabilize
+
+        # Encode file data as base64
+        base64_data = base64.b64encode(file_data).decode('ascii')
+
+        # Send upload command
+        command = f"UPLOAD {filename} {file_size}\n"
+        print(f"Sending command: {command.strip()}")
+        ser.write(command.encode('ascii'))
+
+        # Send base64-encoded file data
+        print("Sending file data...")
+        ser.write(base64_data.encode('ascii'))
+        ser.write(b'\n')
+
+        # Send END marker
+        ser.write(b'END\n')
+        print("Upload complete, waiting for confirmation...")
+
+        # Read response from device
+        start_time = time.time()
+        response_lines = []
+        while time.time() - start_time < 10:  # 10 second timeout
+            if ser.in_waiting > 0:
+                line = ser.readline().decode('utf-8', errors='ignore').strip()
+                if line:
+                    print(f"  << {line}")
+                    response_lines.append(line)
+
+                    # Check for success
+                    if line.startswith('OK'):
+                        print(f"✓ File written successfully!")
+
+                    if line.startswith('LAUNCHED'):
+                        game_name = line.split(' ', 1)[1] if ' ' in line else filename
+                        print(f"✓ Game '{game_name}' launched!")
+                        ser.close()
+                        return True
+
+                    # Check for error
+                    if line.startswith('ERROR'):
+                        print(f"✗ Upload failed: {line}")
+                        ser.close()
+                        return False
+
+        print("Warning: No response received from device")
+        ser.close()
+        return False
+
+    except serial.SerialException as e:
+        print(f"Serial error: {e}")
+        return False
+    except Exception as e:
+        print(f"Unexpected error: {e}")
+        return False
+
+def main():
+    if len(sys.argv) < 2:
+        print(__doc__)
+        print("\nAvailable serial ports:")
+        try:
+            import serial.tools.list_ports
+            for port in serial.tools.list_ports.comports():
+                print(f"  {port.device}: {port.description}")
+        except ImportError:
+            print("  (install pyserial to see available ports)")
+        sys.exit(1)
+
+    lua_file = sys.argv[1]
+    serial_port = sys.argv[2] if len(sys.argv) > 2 else None
+
+    success = upload_game(lua_file, serial_port)
+    sys.exit(0 if success else 1)
+
+if __name__ == '__main__':
+    main()