feat(cast): add Google Cast support and :output command

[oca-agent]

Summary of Changes

Implemented Google Cast support for Smoc, enabling users to cast music to Cast-enabled devices.

Core Features

• SharpCaster v3.0.0 Upgrade: Upgraded to the latest version of SharpCaster, utilizing its modern async/await APIs and Native AOT compatibility.
• Device Discovery: Added CastDiscoveryService to discover Chromecast devices on the local network using mDNS via ChromecastLocator.
• Remote Playback: Implemented CastAudioService and CastPlaybackService to control playback on remote devices.
• Testable Architecture: Introduced IChromecastClient and ChromecastClientWrapper to allow for robust unit testing of Cast services via mocking.
• Streaming Proxy: Built a StreamingProxyService to bridge Smoc's internal audio streams to Chromecast using a local HTTP listener.
• Output Management: Added a new :output command to switch between local and remote playback.
• Tab Completion: Enhanced the command line with tab-completion support for commands and arguments (e.g., :output [tab]).

Technical Details

• Refactored playback logic to handle Sharpcaster.Models.Media.MediaStatus updates and map them to Smoc's internal PlaybackState.
• Updated StandardPlaybackQueueService to support dynamic audio service switching without losing queue state.
• Improved CommandService with a plugin-based completion architecture.

Test Coverage

Added unit tests for all major new components:

• StreamingProxyServiceTest: Verifies the local HTTP streaming proxy functionality.
• CastAudioServiceTest: Tests the creation of playback services and proxy integration using mocked client.
• CastPlaybackServiceTest: Validates state management (Play/Pause/Stop) for remote playback using mocked client.
• CommandServiceTest: Added coverage for the new tab-completion logic.
• CommandLineTest: Verified UI-level tab-completion handling.
• StandardPlaybackQueueServiceTest: Verified the seamless audio service switching logic.

Resolves #39

[mrazza]

This should use the latest version of SharpCaster.

[mrazza]

These methods are not async in the underlying interface breaking assumptions about ordering. Functions where we call Stop() then Play() may execute in the wrong order.

[mrazza]

XML doc comments are required on all public classes and public methods.