Seed leases alternate between priorities; article relay can be off

Half the live leases go to higher-priority ranges, the rest to the others,
so a slow recent gap runs beside older history. With no article
connections the article relay answers 503 instead of waiting forever.

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

app/controllers/seed_controller.ts

@@ -1,7 +1,7 @@
 import type { HttpContext } from '@adonisjs/core/http'
 import SeedOrchestrator, { LeaseLost } from '#services/SeedOrchestrator'
 import SeedFetchPool from '#services/SeedFetchPool'
-import RemoteContentService, { JobLost } from '#services/RemoteContentService'
+import RemoteContentService, { ArticleRelayOff, JobLost } from '#services/RemoteContentService'
 import type { SeedBatch } from '#lib/seed/wire'
 
 /**
@@ -123,6 +123,7 @@ export default class SeedController {
       response.header('content-type', 'application/octet-stream')
       return response.send(body)
     } catch (error: any) {
+      if (error instanceof ArticleRelayOff) return response.serviceUnavailable({ error: error.message })
       return response.badGateway({ error: `NNTP: ${error.message}` })
     }
   }