Add title, user-agent, refer and origin fields to IPC payloads sent
when opening MPV/VLC players and when launching streams from effects.
Replace legacy userAgent property with standardized 'user-agent' key and
consistently include referer and origin from channel.http. This ensures
external players receive correct HTTP header metadata and stream titles
for proper request handling and display.
Update channel.model to import Channel from the local interface file
instead of the package namespace. This fixes an incorrect module
resolution and keeps the codebase consistent with local typings.
Add a new SidebarView union type ('CHANNELS' | 'PLAYLISTS') to expose
possible sidebar view options for consumers of the shared interfaces.
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