MasterRejection

Recognizes the failures that mean "AVPlayer refused the master playlist", as opposed to the source being unplayable.

The distinction matters because the two look identical from the host's side — an AVPlayerItem that went .failed — but the remedies are opposites: a refused master plays perfectly as a media-direct session (forceMuxedShape), while a genuinely unplayable source has to fall back to Prism. Getting it wrong either way is a user-visible failure, so the codes are named here once instead of being re-typed at each call site.

#The three codes

• -11868 AVErrorNoCompatibleAlternatesForExternallyPausedVideo — every variant was rejected by the compatibility gate. What a dvh1 claim gets from a non-DV display, and what an over-claimed CODECS string gets from a decoder that can't take it.
• -11848 — the SDR-parked-panel rejection: a VIDEO-RANGE=PQ/HLG variant offered to a display that is not going to leave SDR. DisplayCapabilities reads readiness optimistically (Match Content is the common case and cannot be distinguished from Match-Content-off), so this is the code that catches the optimism being wrong.
• -1002 NSURLErrorUnsupportedURL — every variant was filtered while parsing the master, so AVPlayer never fetched a media playlist at all and reports the manifest URL as unsupported. An HDR variant with no FRAME-RATE is the classic cause (which MasterPlaylistBuilder refuses to emit for exactly this reason), but a served master can still earn it.

Codes are matched across error domains on purpose: -11868/-11848 arrive in AVFoundationErrorDomain while -1002 arrives in NSURLErrorDomain, none of the three collides with a code the other domain uses, and pinning domains would only add a way to miss a match.