Add asciicast recording, replay, and live streaming

[Marc-André Moreau (mamoreau-devolutions)]

Summary

• add per-tab asciicast recording, save/export, and read-only replay workflows
• support asciicast v2 and v3 parsing, serialization, timing, and initial visible-screen capture
• add reusable WebSocket streaming for official asciinema v2/v3 and DVLS-compatible v2 endpoints
• expose Start streaming... and Stop streaming through the command palette with a paste-URL/protocol dialog
• protect unsaved recordings during tab/window closure and document the app and NuGet APIs

Validation

• dotnet build Devolutions.Terminal.slnx -c Debug --nologo
• Settings action tests: 27 passed
• App action tests: 28 passed
• UI tests: 2 passed
• Control streaming tests: 10 passed
• real official asciinema-server v3 producer stream, live playback, clean stop, and persisted recording