feat(media): the movie-library relayout toolchain — census, plan, executor

The movie library on the entropy volume is release-folded: the video inside
`Some.Movie.2019.1080p…-FOO/` is named after the release, and Jellyfin matches
a movie by folder and file name, so the noise cost posters, extras and versions.
Three scripts own the fix, and nothing else in the repo moves a media file.

  * media-census.py  the read-only inputs: a stat pass, an ffprobe header pass
                     (nice'd, so it is safe beside a live endpoint), and the
                     Plex metadata cache read that outranks any filename guess
  * media-plan.py    the Jellyfin-format planner: one folder per movie, the
                     video named exactly like the folder, extras in the
                     canonical subfolders, copies of one film as versions. It
                     opens no media file, so a whole-library plan costs seconds,
                     and it ends in gates — bad-names, occupied, double-claim,
                     left-unmoved, unplanned — that must all read zero before a
                     human points the executor at 24 TB
  * media-apply.py   the executor: rename(2) only, the intent fsynced to a
                     write-ahead journal BEFORE the move it authorises, so an
                     interrupted run is finishable and every run is undoable.
                     Refusals are all-or-nothing and it never overwrites a file

Laws the fixture pins (tests/media_relayout.bats, 16 tests, each proven red
against a reverted copy of the rule it guards):

  * a Plex year of 0 means "indexed, never matched" — trusting it produced
    folders "Title (0)": items with no year, no poster, no identity
  * a Plex title carrying "/" is sanitised, or "V/H/S/2" became a five-level
    tree neither matcher reads as a movie
  * a folder inside a movie's folder is bonus territory even when its name is
    misspelled ("Exrtas"), unless the file's own name carries another year
  * matching words split on everything but a letter or digit — the earlier
    tokenizer left "(1960)/extras" glued, so a film could not be found by the
    folder holding it and one box set's featurettes drifted into a neighbour
  * a name with no words in it is bonus material, never a movie folder named 1

Docs: the runbook page owns the procedure, the gates and the rollback; AGENTS.md
links it from the runbook index and the summary table.

serverAppConfigs-docs/index.md

@@ -51,6 +51,7 @@ is a locator: one row, one clause, no numbers.
 | [[Entropy Volume]] | The Dankserver entropy volume is a RAID-backed LUKS filesystem mounted at |
 | [[Jellyfin]] | Jellyfin on Dankserver: quadlet unit, entropy-volume data layout, ports, client access, hardware-transcode status. |
 | [[mariadb]] | The MariaDB backend for RomM: quadlet unit, network alias, env-file secret handling, and the backup path. |
+| [[Media Relayout]] | Census, plan and apply the movie library into Jellyfin format: the gates to read, and the rollback. |
 | [[Plex]] | Plex Media Server is a **containerized media server on Dankserver**: a podman |
 | [[redis]] | The Redis cache and task queue for RomM: quadlet unit, network alias topology, and the backup path. |
 | [[RomM]] | RomM (ROM Manager) is a self-hosted ROM library manager and player. |