Keep only the 7z tails of a release's highest volume

The live tail reads an upload in pieces while it is posted, and each
piece queued a 7z-tail candidate for the last volume it had seen so far
(release 306905984: seven, for .002-.008). Only the last volume's end
holds the 7z listing. When candidates are stored, and when releases are
merged, waiting tails below the release's highest volume are deleted.
All tails of the highest volume stay: a piece that saw only part of it
queued a segment that is not its last. RAR is unaffected: it lists its
files in the first volume's header and gets no tail candidate.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/services/par2_merger.ts

@@ -4,6 +4,7 @@ import { par2ReleaseName } from '#lib/release/index'
 import { looksRandom } from '#lib/release/random'
 import { SidecarFolder } from '#services/sidecar_folder'
 import { Par2Pruner } from '#services/par2_pruner'
+import { pruneSevenZipTails } from '#services/seven_zip_tails'
 
 /** Releases of a set further apart than this (posted) aren't one upload: a repost is merged separately (decision d). */
 const MAX_SPREAD_MS = 48 * 3600 * 1000
@@ -341,6 +342,8 @@ export class Par2Merger {
          WHERE r.id = ? AND r.settled_at IS NOT NULL AND pc.release_id = r.id AND pc.status = 'waiting' AND NOT pc.ready`,
         [target.id]
       )
+      // The members' 7z tails together: those below the highest volume go.
+      await pruneSevenZipTails(trx, [target.id])
       // A set held by the target already, or by two of the others (a par2 and its repost), isn't held twice (every
       // round failed on the primary key from 20:28 UTC on 2026-10-12; LOG.md 2026-10-12 (30)).
       await trx.rawQuery(