Prober: claim range per value of unreadable, from the index ends

Over unreadable >= false Postgres walked every waiting entry of the kind:
2.5 minutes a claim at 28M archive candidates, the prober idle every other
minute. Per value each min and max is one end of the ready index (56 ms).

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

tests/functional/prober.spec.ts

@@ -0,0 +1,26 @@
+import { test } from '@japa/runner'
+import db from '@adonisjs/lucid/services/db'
+import testUtils from '@adonisjs/core/services/test_utils'
+import { Prober } from '#services/prober'
+
+test.group('Prober', (group) => {
+  group.each.setup(() => testUtils.db().withGlobalTransaction())
+
+  test('a claim takes each tier: the readable tiers also take unreadable candidates, a kind with only one of them too', async ({ assert }) => {
+    const [row] = await db
+      .table('releases')
+      .insert({ release_key: 'pb'.padEnd(40, '0'), identity_key: 'pb'.padEnd(40, '0'), name: 'pb', source: 'subject', groups: '[]', files: 3 })
+      .returning('id')
+    const candidate = (kind: string, unreadable: boolean, ready = true) => ({
+      release_id: row.id, kind, message_id: `<${kind}-${unreadable}-${ready}@x>`, file: kind, ready, unreadable,
+    })
+    // One per kind, so each tier's id range is a single id (the slices' starts aren't random then).
+    await db.table('probe_candidates').multiInsert([candidate('lone', true), candidate('par2', true), candidate('archive', false), candidate('7z-tail', false, false)])
+
+    const prober = new Prober() as any
+    await prober.claimTiers()
+    assert.sameMembers(prober.queue.map((c: { kind: string }) => c.kind), ['lone', 'par2', 'archive'])
+    const status = Object.fromEntries((await db.from('probe_candidates').select('kind', 'status')).map((c) => [c.kind, c.status]))
+    assert.deepEqual(status, { 'lone': 'taken', 'par2': 'taken', 'archive': 'taken', '7z-tail': 'waiting' })
+  })
+})