XoverClient times replies only, not idle time between commands

A seeding node that waited over two minutes for the seed API (restarting)
had its idle NNTP connection closed by its own timeout, and gave its range
back. Now the timeout runs only while a reply is awaited.

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

tests/unit/xover_client.spec.ts

@@ -73,4 +73,17 @@ test.group('nntp / XoverClient', () => {
       }
     })
   }
+
+  test('idle time between commands does not count against the reply timeout', async ({ assert }) => {
+    const { port, close } = await server()
+    const client = await XoverClient.connect({ host: '127.0.0.1', port, user: 'u', password: 'p', compress: true, timeoutMs: 200 })
+    try {
+      await client.group('a.b.test')
+      await new Promise((resolve) => setTimeout(resolve, 500))
+      assert.lengthOf(await client.xover(101, 102), 2)
+    } finally {
+      client.close()
+      close()
+    }
+  })
 })