Complete archive listings by walking RAR headers, at low priority

Inspection lists only the entries whose headers are in the first segment
of a first volume. A walk hops from header to header, fetching one segment
per entry and volume, in its own queue (one job per collection worker) on
NNTP connections inspection isn't waiting for. content:walk-archives queues
releases inspected earlier (CONCEPT D40).

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

database/migrations/1768620765170_release_contents_walked.ts

@@ -0,0 +1,14 @@
+import { BaseSchema } from '@adonisjs/lucid/schema'
+
+/** When an archive walk (CONCEPT.md D40) looked at a release, so it isn't walked again. */
+export default class extends BaseSchema {
+  async up() {
+    this.schema.alterTable('releases', (table) => {
+      table.timestamp('contents_walked_at', { useTz: true })
+    })
+  }
+
+  async down() {
+    this.schema.alterTable('releases', (table) => table.dropColumn('contents_walked_at'))
+  }
+}