Merge #179: size bands are per episode

Closes #179

DESIGN.md

@@ -77,7 +77,8 @@ Policy
   required_audio          rule set, see §5.2
   dub_blacklist           [pt-BR]
   hdr_rules               see §5.3
-  size_bands              per resolution: floor, target, penalty curve
+  size_bands              per resolution: floor, target, penalty curve,
+                          all per episode (§5.5)
   resolution_pref         [2160p, 1080p]
   source_weights          small tiebreaker
 
@@ -284,6 +285,28 @@ remux scores badly but stays eligible, so it is picked when it is the only
 option. The floor matters — unbounded "smaller is better" selects a 3 GB 4K
 encode that looks like mud.
 
+**A band describes one episode.** For a movie the question never arises — one
+release is one film. For TV a release may carry a single episode, several, or a
+whole season, and the shipped TV numbers are episode numbers: a 1080p target of
+2 GiB is what one episode should weigh, not a ten-episode pack. So a release is
+measured by its size divided by the number of episodes it covers, and that
+per-episode figure is what both the target penalty and the floor are compared
+against. A 20 GiB pack of ten episodes is scored as 2 GiB and sits at target,
+not ten times above it.
+
+The floor takes the same figure. It is a hard reject rather than a penalty, so
+comparing a pack's total against an episode-sized floor lets every pack through
+untested — wrong in the opposite direction from the target penalty. The floor
+exists to keep a 3 GB 4K encode out, and a pack of ten such encodes has to fail
+it just as plainly.
+
+**An unknown episode count is one episode.** A release matched before its
+season's episodes have been revealed by a metadata refresh has nothing to divide
+by, and the rule does not guess a number: the divisor is 1 and the release is
+measured by its full size. That is the behaviour today, and it makes a pack look
+oversized rather than undersized — it fails toward rejecting a good pack rather
+than grabbing a bad one, and the next search after a refresh has the real count.
+
 Source tier (`Remux > BluRay > WEB-DL > WEBRip > HDTV`) survives as a small
 tiebreaker. Seeders are log-scaled and small: enough to complete, past that it
 does not matter. Telesync, CAM and screener are **hard filters**, not low