feat: queue only targets still waiting for a file

The needs-a-decision queue had no liveness condition on the season lane
and none at all in the API reader, so a season pack that hard-failed
twice, fell back to per-episode grabbing exactly as §6.2 intends, and was
then fully acquired kept notifying for 30 days, and
`GET /api/queues/attention` listed titles the daemon never notified on.

DESIGN.md §5.7 now states the third face of the same rule alongside the
count and the window: a movie or an episode is queued while `wanted` and
not `available`; a season, holding no intent of its own (§4.1), while at
least one of its episodes is. Both readers apply it on all three lanes.

`just ci` passed through the gate.

DESIGN.md

@@ -395,6 +395,22 @@ guard retries at worst weekly (§6.2) — and stays queued for exactly as long a
 it is genuinely broken. Nothing is dismissed by hand and no acknowledgement
 state is stored, so there is no second thing to keep correct.
 
+**Only a target still waiting for a file is queued.** The count and the window
+are one rule seen twice — the queue is meant to be visited and emptied — and
+this is its third face: a failure history queues a target only while that
+target still has a gap to fill. A movie or an episode is queued while it is
+`wanted` and not `available`. A season holds no intent of its own (§4.1), so it
+is queued while at least one of its episodes is still wanted and still without
+a file. A season pack that hard-failed twice, fell back to per-episode grabbing
+exactly as §6.2 says it should, and was then fully acquired leaves at once
+rather than waiting out the 30 days — that is the system working, not a
+decision. A target that is still broken keeps producing failures and stays.
+
+The same rule applies on all three lanes and in both readers.
+`GET /api/queues/attention` (§9.3) and the `ntfy` notification (§9.5) are two
+views of one queue; filtering differently tells the operator two different
+stories on two channels.
+
 ## 6. Sourcing
 
 ### 6.1 Prowlarr, per-indexer Torznab