The par2 prune's cursor is (created_at to the microsecond, set_id): 20k sets of one flush share a created_at

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

database/migrations/1770000004300_worker_cursors_key.ts

@@ -0,0 +1,16 @@
+import { BaseSchema } from '@adonisjs/lucid/schema'
+
+/**
+ * worker_cursors.key: a tie-breaker after `at`. The par2 pruner's cursor was a timestamp alone, read back to the
+ * millisecond: 20,000 sets of one prober flush share created_at 2026-10-15 14:38:39.883984, and every round took the
+ * same batch again (LOG.md 2026-10-17 (73)). Now (at to the microsecond, set_id).
+ */
+export default class extends BaseSchema {
+  async up() {
+    this.schema.raw(`ALTER TABLE worker_cursors ADD COLUMN IF NOT EXISTS key text`)
+  }
+
+  async down() {
+    this.schema.raw(`ALTER TABLE worker_cursors DROP COLUMN IF EXISTS key`)
+  }
+}