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>

lib/content/index.ts

@@ -2,6 +2,6 @@
  * Content recognition by magic bytes, independent of AdonisJS.
  */
 export { sniffContentType, type ContentType } from './sniff.js'
-export { isArchiveStart, isLaterVolume } from './archive_names.js'
+export { isArchiveStart, isLaterVolume, rarVolume } from './archive_names.js'
 export { parseSfv, sfvReleaseName, type SfvEntry } from './sfv.js'
 export { NICOVIDEO_FILE, NICOVIDEO_RELEASE, nicovideoInfo, nicovideoReleaseName, zstdPrefix, tarEntries, type NicovideoInfo } from './nicovideo.js'