External-JSON playout channels build their own /media/plex/{server}/{plexFile}
URL in ExternalJsonPlayoutItemProvider.StreamRemotely and the handler assigns it
without routing through ValidatePlayoutItemPath, so the #473 class survived here:
a media item gone from the server 404s under ffmpeg (exit 8) and the same dead
item is re-selected for its whole slot.
Route StreamRemotely through the same IRemoteStreamProber seam #473/PR #479 added
for the generated-playout path. Probe runs before the Plex metadata round-trip
(the URL needs only server.Id + plexFile), so a gone item skips it. An unavailable
stream returns PlayoutItemNotAvailableFromMediaServer, which the handler already
maps to a real-error card. The fail-open policy (redirected-404 only) lives inside
IRemoteStreamProber, so this second call site duplicates only the decision to probe.
Tests: ExternalJsonPlayoutItemProviderTests pins both directions; proven non-vacuous
by neutralizing the probe. docs/decisions.md gets a #480 entry closing the #473
scope gap (append-only: the old #473 entry is cross-referenced, not edited).
fixes#480
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
timothyandClaude Opus 4.8