docs(vault): the scan pages name their drivers, and a class no screen sees

Plex.md and Jellyfin.md keep every law and point at the driver that now carries
them, so the procedure has one owner and the pages keep the failure signatures.
Jellyfin.md also records where `jellyfin.db` actually lives on this host (the
quadlet's config bind, not the stock path) and demotes `immutable=1` on the
`ApiKeys` read to the `-shm` fallback, because the database is WAL and
`immutable` skips the log. Plex.md gains the live section keys and the
`scanned_at == scannedAt` fact.

Media Relayout.md's hand-off after an apply names both drivers and states the
ordering law: Jellyfin first and alone, since its one door walks every library
while Plex forks a scanner per section, and the array is what both share.

Media Duplicate Prune.md gains the guard the 2026-11-04 hold taught: 32 files
carrying real film titles were 8-20-second h264 clips (49 MiB, 25 of them in a
`_release-group watermarks/` folder), invisible to every duplicate screen
because nothing shares their size and the feature-length guard hides them. The
census that finds the next batch is a duration floor, not a hash.

serverAppConfigs-docs/Dankserver/Media Duplicate Prune.md

@@ -151,6 +151,16 @@ Each of these is a file that would have been destroyed without it:
 - Media containers only. Grouping every extension buries the report in subtitle
   and cover pairs — and a duration guard that appears to fire on 720 groups is
   counting subtitles, not protecting films.
+- **A short file named after a film is promotion, not a movie.** Thirty-two files
+  in `Movies` carried real titles (`The Descent (2005) - SD.mkv`) and were
+  8–20-second h264 clips — 640×360, 1024×576 or 1280×720, 49 MiB all together,
+  25 of them in a `_release-group watermarks/` folder and the rest at the library
+  root or inside one film's folder. No duplicate screen ever catches them: nothing
+  shares their size, and the feature-length guard above makes them invisible to the
+  similar-title pass too. Held as `.AGENTTRASH/20261104-promo-clips`, journalled at
+  `/mnt/entropy/.media-campaign/promo-hold.jsonl`. The census that finds the next
+  batch is a duration floor, not a hash: a video under a minute on a name that
+  reads like a feature is advertising.
 
 ## The hold