Prober: claim from random points of the queue, not in id order

In id order the prober went group by group, and some groups' articles
take 0.6-3 s each (a.b.zogg 2016; repeated fetches the same, pipelining
4 deep no faster), where a sample across all years takes 20-60 ms for
most: 7 articles/s on 6 connections, against 67/s in its first minutes.
A claim now takes 20 slices from random points (353 ms per 200).
tools/body_timing.ts: BODY time for the oldest and newest candidates.

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

tools/body_timing.ts

@@ -0,0 +1,37 @@
+/**
+ * BODY timing by article age: candidates' first articles, oldest and newest
+ * posted, fetched one at a time on one connection (status line, then the
+ * rest), with the release's posting date.
+ *
+ *   node --env-file=.env --import=@poppinss/ts-exec tools/body_timing.ts [n]
+ */
+// @ts-ignore pg has no types here
+import pg from 'pg'
+import { XoverClient } from '#lib/nntp/index'
+
+const n = Number(process.argv[2] ?? 8)
+const env = process.env
+const db = new pg.Client({ host: env.DB_HOST, port: Number(env.DB_PORT ?? 5432), user: env.DB_USER, password: env.DB_PASSWORD, database: env.DB_DATABASE })
+await db.connect()
+const pick = async (order: string) =>
+  (await db.query(`SELECT pc.message_id, r.posted_at FROM probe_candidates pc JOIN releases r ON r.id = pc.release_id WHERE pc.kind = 'lone' AND r.posted_at IS NOT NULL ORDER BY r.posted_at ${order} LIMIT $1`, [n])).rows
+const client = await XoverClient.connect({ host: env.NNTP_HOST!, port: Number(env.NNTP_PORT ?? 563), user: env.NNTP_USER, password: env.NNTP_PASSWORD, secure: (env.NNTP_SECURE ?? 'true') !== 'false', compress: false, timeoutMs: 120_000 })
+for (const [label, rows] of [['oldest', await pick('ASC')], ['newest', await pick('DESC')]] as const) {
+  let total = 0
+  for (const r of rows) {
+    const at = performance.now()
+    let size = 0
+    try {
+      size = (await client.body(r.message_id)).length
+    } catch (e: any) {
+      size = -1
+      console.log(`  ${e.message}`)
+    }
+    const ms = performance.now() - at
+    total += ms
+    console.log(`${label} ${new Date(r.posted_at).toISOString().slice(0, 10)} ${(ms / 1000).toFixed(2)} s ${(size / 1000).toFixed(0)} kB`)
+  }
+  console.log(`${label}: ${(total / rows.length / 1000).toFixed(2)} s an article`)
+}
+client.close()
+await db.end()