Tiny-archive rule; the ladder's discard by index; the namer in chunks

The tiny-archive rule (dropTinyArchives, both indexers): a settled single
archive of one article and 2-100 kB under a release-like name, spaces
allowed, outside the exempt groups and without an e-book, subtitle,
crack, cover or sidecar word: the 2015-17 exe-stub flood in miniature,
1.66M catalog rows (LOG.md (131), (133)).

PendingLadder.discard scanned every waiting row against the dropped
signatures and classes, 9+ minutes a sweep inside the claim, stalling
every lane: now driven from the dropped classes and signatures into the
indexes. The namer feeds the indexer the span's overview text chunk by
chunk (one string of it topped V8's limit) and gives up spans over 3M
articles. Migration 7000: a partial index on the taken probe candidates
for the prober's start.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

database/migrations/1770000007000_probe_candidates_taken_index.ts

@@ -0,0 +1,20 @@
+import { BaseSchema } from '@adonisjs/lucid/schema'
+
+/**
+ * The prober's start puts a previous run's claims back (probe_candidates status taken → waiting), which scanned
+ * the 7.8 GB candidates table on the HDD for 4 minutes after every deploy (LOG.md (133)): a partial index on the
+ * few taken rows makes it instant.
+ */
+export default class extends BaseSchema {
+  static disableTransactions = true
+
+  async up() {
+    this.schema.raw(
+      `CREATE INDEX CONCURRENTLY IF NOT EXISTS probe_candidates_taken_idx ON probe_candidates (id) WHERE status = 'taken'`
+    )
+  }
+
+  async down() {
+    this.schema.raw(`DROP INDEX CONCURRENTLY IF EXISTS probe_candidates_taken_idx`)
+  }
+}