fix(channels): the Length column shows the sum alone

The "+N without length" line did not fit the 4.5 rem column (88 px of
text in a 56 px cell) and spilled into Tags. The owner wants no such
line there: the cell shows the summed hours, and the channel list no
longer sends a count nothing reads. A playlist's total keeps it.

backend/app/catalog/models.py

@@ -125,7 +125,7 @@ LIVE_OR_UPCOMING = ("live", "upcoming")
 # the stream has run (measured on prod, 2026-11-06: 122,962,914 s), and one such video made a Watch
 # later total read 44,073 hours. YouTube caps an upload at 12 hours, so nothing real is lost. Such a
 # length is unknown wherever a length is used: the API sends none (`Video.length_seconds`), sums leave
-# it out and count it as `live_without_length`, and the duration filter, sort and Home budget never
+# it out (a playlist's counts it as `live_without_length`), and the duration filter, sort and Home budget never
 # match it. The raw `duration_seconds` stays for what it does prove — that the video is not a Short —
 # and for the jobs that ask whether YouTube has answered yet (test_video_length holds who reads it).
 LENGTH_MAX_S = 24 * 3600