Prober: pipelined bodies, merge-first order, a probe cache across resets

- XoverClient.bodies: PROBE_PIPELINE (8) BODY commands per connection at
  once, replies read in order (one at a time it ran 3-10 articles/s on 6
  connections against a queue of 1M).
- Claims in tiers: lone files first, then par2 sets and archives of
  releases without a readable name (what the par2 merge needs), then those
  of readable releases.
- probe_cache: final answers by message-id (status, inspection with the
  16 KiB hash and par2 file list), PROBE_VERSION 2. A reset empties the
  probe queue, not the cache; recreated candidates of probed articles are
  answered from it without the news server.

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

lib/nntp/xover_client.ts

@@ -246,6 +246,28 @@ export class XoverClient {
     })
   }
 
+  /**
+   * Several bodies, pipelined: every BODY is sent at once and the replies read in order, so one round trip
+   * covers them all (one at a time, a connection waited ~0.1–2 s per article: 3–10 articles/s on 6; LOG.md
+   * 2026-10-12 (16)). A missing article (430, 423) is null.
+   */
+  async bodies(messageIds: string[]): Promise<(Buffer | null)[]> {
+    return this.timed(async () => {
+      this.sock.write(messageIds.map((m) => `BODY ${m.startsWith('<') ? m : `<${m}>`}\r\n`).join(''))
+      const out: (Buffer | null)[] = []
+      for (let i = 0; i < messageIds.length; i++) {
+        const reply = await this.line()
+        if (reply.startsWith('430') || reply.startsWith('423')) {
+          out.push(null)
+          continue
+        }
+        await this.expect(reply, ['222'])
+        out.push(await this.rawBody())
+      }
+      return out
+    })
+  }
+
   /** A multi-line body up to "\r\n.\r\n", as bytes, the terminator cut off. */
   private async rawBody(): Promise<Buffer> {
     let searched = 0