Seed relay fetches plain overviews by default

For 2026 a.b.ath articles Eweka's gzip replies have a long tail (p90 12.4 s
per 20k vs 3.9 s plain; 6.1k vs 10.5k headers/s). SEED_NNTP_COMPRESS turns
compression back on; plain replies are deflated for nodes asynchronously.

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

lib/nntp/xover_client.ts

@@ -1,6 +1,9 @@
+import { promisify } from 'node:util'
 import net from 'node:net'
 import tls from 'node:tls'
-import { deflateSync, unzipSync } from 'node:zlib'
+import { deflate, deflateSync, unzipSync } from 'node:zlib'
+
+const deflateAsync = promisify(deflate)
 
 export interface XoverClientOptions {
   host: string
@@ -100,7 +103,9 @@ export class XoverClient {
       const reply = await this.command(`XOVER ${from}-${to}`)
       if (reply.startsWith('420') || reply.startsWith('423')) return deflateSync(Buffer.alloc(0))
       await this.expect(reply, ['224'])
-      return reply.includes('COMPRESS=GZIP') ? (await this.compressedRaw()).raw : deflateSync(Buffer.from(await this.plainBody()))
+      if (reply.includes('COMPRESS=GZIP')) return (await this.compressedRaw()).raw
+      // Plain replies (the relay's default): compressed off the event loop, at the fastest level.
+      return deflateAsync(Buffer.from(await this.plainBody()), { level: 1 })
     })
   }