Seed relay: nodes get their headers through the seed API

The seed API keeps a pool of NNTP connections (SEED_NNTP_CONNECTIONS) and
serves GET /api/v1/seed/ranges/:id/chunk?from=&to= for leased ranges:
the gzip stream the news server sent, passed on unopened. seed:node fetches
that way by default (SEED_FETCH=relay), so a node needs only a token and
SEED_CONNECTIONS; SEED_FETCH=direct keeps its own NNTP connections. All
fetching then comes from the indexer's IP (the account allows two).

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

app/controllers/seed_controller.ts

@@ -1,5 +1,6 @@
 import type { HttpContext } from '@adonisjs/core/http'
 import SeedOrchestrator, { LeaseLost } from '#services/SeedOrchestrator'
+import SeedFetchPool from '#services/SeedFetchPool'
 import type { SeedBatch } from '#lib/seed/wire'
 
 /**
@@ -31,6 +32,27 @@ export default class SeedController {
     })
   }
 
+  /**
+   * GET /api/v1/seed/ranges/:id/chunk?from=&to= → the overviews of those
+   * articles as a zlib/gzip stream (relay nodes fetch through the indexer).
+   */
+  async chunk({ seedNode, params, request, response }: HttpContext) {
+    if (SeedFetchPool.size === 0) return response.serviceUnavailable({ error: 'Relay is off (SEED_NNTP_CONNECTIONS=0); fetch directly' })
+    const from = Number(request.input('from'))
+    const to = Number(request.input('to'))
+    if (!Number.isSafeInteger(from) || !Number.isSafeInteger(to)) return response.badRequest({ error: 'Expected ?from=&to=' })
+    return this.leased(response, async () => {
+      try {
+        const raw = await SeedOrchestrator.chunk(seedNode.id, Number(params.id), from, to)
+        response.header('content-type', 'application/octet-stream')
+        return response.send(raw)
+      } catch (error) {
+        if (error instanceof RangeError) return response.badRequest({ error: error.message })
+        throw error
+      }
+    })
+  }
+
   /** POST /api/v1/seed/ranges/:id/done */
   async done({ seedNode, params, response }: HttpContext) {
     return this.leased(response, async () => {