Implement Media Capture API

[General-Fault]

Implement full Media Capture and Streams API (MediaStream, MediaStreamTrack, MediaDevices, constraints, DTOs).

Scope

• Include: Full Media Capture API surface including MediaStream, MediaStreamTrack, MediaDevices, all constraint types, and related DTOs
• Exclude: WebRTC API (RtcPeerConnection, RtcRtpSender, etc.), full VideoRenderer implementation
• Platform: Windows only (C++/CLI)

Implementation Order (Dependency Chain)

1. DTO & enum marshalling + EnumerateDevices
2. Constraint type marshalling (all wrapper types, EchoCancellation, etc.)
3. GetUserMedia with full constraint handling
4. MediaStreamTrack constraint methods (GetCapabilities, GetSettings, ApplyConstraints)
5. Complete MediaStream & MediaStreamTrack interop

Key Design Decisions

• Use existing marshalling patterns from MarshalIceServer.h, MarshalMediaConstraints.h as templates
• Leverage C++ smart pointers (unique_ptr, shared_ptr, scoped_refptr, ManagedScopedRefPtr)
• Follow copy/move semantics for efficiency
• All constraint marshalling in dedicated header (single responsibility)
• DTOs are pure managed records — marshalling converts native → managed, no round-trip
• Enums use MarshalEnums.h pattern (switch or bidirectional map)

Child Issues

See numbered child issues linked below.