Added ChannelId to PlayoutNameViewModel and all 6 construction sites
(Mapper, GetPlayoutByIdHandler, and the Update{,Scripted,ExternalJson,Sequential}
PlayoutHandler commands), plus the list DTO PlayoutListItemResponseModel and the
PlayoutController list projection. Regenerated OpenAPI (v1.json) and the TS client
(v1.d.ts); endpoint-index.md unchanged (no endpoint/operation delta). Simplified
PlayoutsScreen resetSelectedChannel to key directly on selectedSummary.channelId
instead of resolving via channelStates. Updated controller + SPA tests.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>