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>

tests/functional/seed_api.spec.ts

@@ -144,6 +144,20 @@ test.group('Seed API', (group) => {
     assert.include(leased.body().range, { start: 101, end: 200 })
   })
 
+  test('priorities take turns: half the leases go to the higher priority', async ({ client, assert }) => {
+    const token = await SeedOrchestrator.issueToken('turns-node')
+    const auth = { authorization: `Bearer ${token}` }
+    await db.table('seed_ranges').insert([
+      { group_name: 'alt.binaries.test', start_id: 1, end_id: 100, next_id: 1 },
+      { group_name: 'alt.binaries.test', start_id: 101, end_id: 200, next_id: 101 },
+      { group_name: 'alt.binaries.test', start_id: 1001, end_id: 1100, next_id: 1001, priority: 1 },
+      { group_name: 'alt.binaries.test', start_id: 1101, end_id: 1200, next_id: 1101, priority: 1 },
+    ])
+    const starts: number[] = []
+    for (let i = 0; i < 4; i++) starts.push((await client.post('/api/v1/seed/lease').headers(auth)).body().range.start)
+    assert.deepEqual(starts, [1001, 1, 1101, 101])
+  })
+
   test('a node inspects a file: lease, probe result, applied here (D41)', async ({ client, assert }) => {
     await QueueService.collectionQueue.drain()
     await QueueService.archiveWalkQueue.drain()