fix(clip): a clip is held to its owner's storage cap, and its limits and failures say the server's truth

- The cut file is measured against what its owner has left, for a YouTube range (whose fetch never
  reads yt-dlp's size ceiling) and for a Plex clip (which fetches nothing), before the fetch and
  again before it is placed; a refusal leaves the asset pending for a Retry.
- A silent Plex file is cut silent; a file the probe cannot read says so.
- A second job on a failed or renamed clip gets the same YouTube diagnosis and the fetched title.
- The "too long" refusal names the server's cap; a contract test holds the client's copies of the
  clip limits to clip.py; the shipped player clients are pinned against the installed yt-dlp.
- One HDR transfer set and one rating_key lookup; job status words from JobStatus; the display-name
  guard sees subscript writes and the clip route; stale comments and types follow the clip job.

backend/app/plex/stream.py

@@ -35,7 +35,7 @@ from app.config import settings
 from app.downloads.edit import encode_thread_cap
 from app.models import PlexItem
 from app.plex import paths
-from app.plex.sync import HW_DECODABLE_CODECS
+from app.plex.sync import HDR_TRANSFERS, HW_DECODABLE_CODECS
 
 log = logs.get_logger(__name__)
 _HLS_ROOT = (
@@ -203,7 +203,8 @@ _HW_DECODABLE = HW_DECODABLE_CODECS
 # plain scale_vaapi=format=nv12 path (Gen 9.5 VPP refuses it) — it needs the OpenCL tonemap graph
 # (_venc_opts tonemap branch) when the OpenCL runtime is present, else software libx264. A 10-bit source
 # WITHOUT one of these transfers is SDR, not HDR, and must not be tone-mapped. See _probe_video_kind.
-_HDR_TRANSFERS = {"smpte2084", "arib-std-b67"}
+# THE single source is plex.sync (a clip's tonemap reads it too).
+_HDR_TRANSFERS = HDR_TRANSFERS
 
 
 # The three source classes that drive the transcode-pipeline choice (see _probe_video_kind).