NNTP shares: the account's connections shared by priority

The coordinator (38) and the prober (8) had a fixed split; with history
paused the coordinator's stood idle while the prober's were its limit.
nntp_shares: each process syncs every 15 s (priority, minimum, what it could
use, what it has open) and gets what it may open: minimums first, then by
priority what each wants, growing only into connections the others closed
or gave up. The pool's size and the prober's lanes follow the grant; the
coordinator doubles its want while work waits for a connection, else asks
for its peak in use and a margin; the prober wants its maximum unless the
queue is dry. Claims scale with the lanes.

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

database/migrations/1770000004400_nntp_shares.ts

@@ -0,0 +1,26 @@
+import { BaseSchema } from '@adonisjs/lucid/schema'
+
+/**
+ * nntp_shares: the account's connections shared by the processes that read articles (app/services/nntp_shares.ts).
+ * Each process's row says what it could use and has open, and what it may open; a row without a heartbeat for a
+ * minute is a process gone (its connections closed with it). The split was fixed per process: with history paused
+ * the coordinator's 38 stood idle while the prober's 8 were the limit (LOG.md 2026-10-18 (75)).
+ */
+export default class extends BaseSchema {
+  async up() {
+    this.schema.raw(`
+      CREATE TABLE IF NOT EXISTS nntp_shares (
+        name text PRIMARY KEY,
+        priority integer NOT NULL,
+        min integer NOT NULL,
+        want integer NOT NULL,
+        open integer NOT NULL,
+        granted integer NOT NULL,
+        heartbeat_at timestamptz NOT NULL DEFAULT now()
+      )`)
+  }
+
+  async down() {
+    this.schema.raw(`DROP TABLE IF EXISTS nntp_shares`)
+  }
+}