This PR adds comprehensive tvOS support to MLX-Swift by updating the Package.swift manifest and providing architecture compatibility for tvOS devices.

Changes

1. Package.swift: Added .tvOS(.v16) to the list of supported platforms
2. GPU.swift: Added tvOS 17.0 to the availability check for the architecture property

Problem

MLX-Swift currently doesn't support tvOS, preventing developers from bringing
on-device ML capabilities to Apple TV applications. When attempting to use MLX-Swift
in a tvOS project:

• The package doesn't declare tvOS support in its manifest
• Compilation fails due to the architecture property being unavailable on older tvOS
  versions

Solution

1. Explicitly declare tvOS v16+ support in Package.swift
2. Add tvOS 17.0 to the #available check since the architecture property is available
   on tvOS 17.0 and later (as per Apple documentation)

Impact

• ✅ Enables MLX-Swift to be imported and used in tvOS projects
• ✅ Maintains backward compatibility with tvOS 16+ (using device.name for older versions)
• ✅ No changes to existing macOS/iOS functionality
• ✅ Opens up on-device ML capabilities for Apple TV apps

Testing

Successfully tested on Apple TV (tvOS 18) with a production app:

• Downloaded and ran Llama 3.2 1B model
• Performed real-time text generation
• No compilation or runtime issues

Use Cases

This enables exciting possibilities for tvOS apps:

• On-device AI assistants for TV interfaces
• Real-time content analysis and recommendations
• Privacy-preserving ML features without cloud dependencies
• Interactive educational content with local language models