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/anchors.js

@@ -47,8 +47,10 @@ function topTagsFor(anchors, recordOf, { mature = false } = {}) {
   const scores = new Map();
   for (const anchor of anchors) {
     const record = recordOf(anchor.anilistId);
-    for (const tag of record?.tags || []) {
-      if (tag.rank < MIN_TAG_RANK || (tag.isAdult && !mature)) continue;
+    for (const tag of Array.isArray(record?.tags) ? record.tags : []) {
+      // A tag without a rank is no evidence of taste, so it must not pass the rank filter.
+      if (!tag || typeof tag !== 'object' || typeof tag.name !== 'string') continue;
+      if (!(tag.rank >= MIN_TAG_RANK) || (tag.isAdult && !mature)) continue;
       const entry = scores.get(tag.name) || { name: tag.name, kind: tag.kind, score: 0 };
       entry.score += anchor.weight;
       scores.set(tag.name, entry);