feat(media): measure a series per episode, and let the tag outrank a borrowed id

media-tvdupes.py censuses a TV library by episode key and never by folder. 10 of
the 25 shows that looked duplicated in the 2026-11-02 census held complementary
halves (Game of Thrones Complete carries no S01 or S08, Modern Family S05 is the
only copy of season 5), so a folder-level verdict would have staged some 340 GB
of unique episodes to recover 54 GiB of true copies.

Show identity comes from the folder's [tvdbid-N] tag, from the tvshow.nfo the
metadata view exposes, or from an operator --ids map. A derived id that
contradicts a tag is dropped and reported, never unioned: Jellyfin's provider
table carries a 2026 special's id on the folder tagged [tvdbid-73838], and
unioning the two makes one show of a 2000 series and a 2026 special whose bigger
files then dominate the original's pilot. Files named by an id key only when the
server's own episode table (the --witness) names them, so a bare number is never
mistaken for an episode.

Seam: tests/media_tvdupes.bats — 12 assertions on which files land in the plan
and which the tool refuses to touch, on a synthetic library.

serverAppConfigs-docs/Dankserver/Media Relayout.md

@@ -138,7 +138,7 @@ HTTPD close without a single byte; and the same HTTPD drops requests that carry
 no `Accept` and client-identifier header (see the scan block above for the form
 that works).
 
-A duplicate prune is the same census and the same proof, with its own keep rules: [[Media Duplicate Prune]].
+A duplicate prune is the same census and the same proof, with its own keep rules — films by title and duration, a series per episode: [[Media Duplicate Prune]].
 
 ## TV in the movie library