fix(media): a series is the name before the episode marker

Keyed on the whole episode title, every episode of a box set became a group of
one and never reached the five-episode size that calls something a series, so
the live run filed 124 Monk episodes as 124 movie folders, each named after its
own episode. ep_of now returns the series — the name before SxxEyy / 1x04 /
Part N — and the planner groups and names the quarantine pile by that series,
so one show is one pile: 'Monk - S05E03 - Mr. Monk and the Big Game' is series
monk. The threshold keeps its job: a lone film named Part 2 stays a film.

Re-planning the live census with this moves nothing differently except the 124
Monk files, which now join the TV pile: 168 episode files across 3 series.

scripts/media-plan.py

@@ -222,8 +222,9 @@ eps = collections.defaultdict(list)
 for r in erows:
     if r["path"] in marks | extras:
         continue
-    if eng.ep_of(r["path"]):
-        eps[eng.key_of(r["title"])].append(r)
+    ep = eng.ep_of(r["path"])
+    if ep:
+        eps[ep[0]].append(r)      # keyed by the SERIES, never the episode title
 tv_keys = {k for k, v in eps.items() if len(v) >= 5}
 tv_set = {r["path"] for k, v in eps.items() if k in tv_keys for r in v}
 # A folder INSIDE a movie's folder is bonus territory even when its own name is
@@ -776,19 +777,17 @@ readmes.append(f"README in {ROOT}: this library was relaid out into Jellyfin's "
                "one-folder-per-movie layout; `_release-group watermarks/`, "
                "`_unsorted files/` and `_unsorted bonus/` hold files no film claims.")
 for key in tv_keys:
-    nm = "_TV needs a TV library - " + collections.Counter(
-        r["title"] for r in eps[key]).most_common(1)[0][0]
-    readmes.append(f"README in {ROOT}/{sanitize(nm)}: these are TV episodes found in "
-                   "the MOVIES library; move the folder to a TV library source, else "
-                   "Jellyfin groups them wrongly as one movie.")
+    readmes.append(f"README in {ROOT}/{sanitize('_TV needs a TV library - ' + key)}: "
+                   "these are TV episodes found in the MOVIES library; move the folder "
+                   "to a TV library source, else Jellyfin groups them wrongly as one "
+                   "movie.")
 
 # --------------------------------------------------------------------- TV
 for key in tv_keys:
     items = eps[key]
-    title = collections.Counter(r["title"] for r in items).most_common(1)[0][0]
     year = collections.Counter(r["year"] for r in items if r["year"] != "?")
     yr = year.most_common(1)[0][0] if year else None
-    base = f"_TV needs a TV library - {sanitize(title)}" + (f" ({yr})" if yr else "")
+    base = f"_TV needs a TV library - {sanitize(key)}" + (f" ({yr})" if yr else "")
     tops = {parts_of(r["path"])[0] for r in items}
     members = sorted([r["path"] for r in items]
                      + [q for q in extras | marks if len(parts_of(q)) > 1