Discovery final review fixes: lean publish, robust scoring, cheap prune (BL-0051)

- Cache prune counts directory entries first and only reads files when over
  the cap; tests for cross-kind prune, schema-mismatch and corrupt entries.
- Scoring tolerates malformed manga.json and cached records (non-list tags,
  object or null relations, non-object items); a tag without a rank no longer
  passes the top-tag filter; authors without an integer AniList id are dropped.
- discovery.json publishes only candidates some feed shows; examined/clipped
  still describe the pool. Tests that asserted the published count equals the
  pool size now check the pool via candidatePool() and the published set
  against the feeds.
- The post-harvest rescore failure test now breaks discovery.json right before
  the publish (via a scraper stand-in) instead of relying on tags: 5, and a
  following successful harvest clears the stale lastError.
- Consent text names everything sent to AniList; paused label mentions admin
  harvests; the UI test asserts the XSS seed instead of skipping it.
- Slot-mix test proves the fresh/outside reservations matter.
- Docs: privacy note, fresh fallback reason, per-period cap, dry-run wording,
  published-candidate rule; plan/spec hygiene and spec status.

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

discovery/anilist.js

@@ -64,7 +64,8 @@ function normalizeMedia(media) {
       ...(media.genres || []).map(name => ({ name, rank: 100, kind: 'genre', isAdult: false })),
       ...(media.tags || []).map(tag => ({ name: tag.name, rank: tag.rank, kind: 'tag', isAdult: !!tag.isAdult }))],
     authors: (media.staff?.edges || [])
-      .filter(edge => STAFF_ROLE.test(edge.role || '') && edge.node?.name?.full)
+      // An author without an integer id could never match a creator seed.
+      .filter(edge => STAFF_ROLE.test(edge?.role || '') && edge.node?.name?.full && Number.isInteger(edge.node.id))
       .map(edge => ({ staffId: edge.node.id, name: edge.node.name.full, role: edge.role })),
     coverUrl: media.coverImage?.extraLarge || null,
     siteUrl: media.siteUrl || null,