The merger keeps its place over a restart (worker_cursors), not from 1970 each deploy

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

tests/functional/par2_merger.spec.ts

@@ -65,6 +65,19 @@ test.group('Par2Merger', (group) => {
     assert.deepEqual(await new Par2Merger().round().then((r) => r.merges), 0)
   })
 
+  test('a restart goes on from the last whole round, kept in worker_cursors', async ({ assert }) => {
+    const hourAgo = new Date(Date.now() - 3600_000)
+    await db.table('par2_sets').insert({ set_id: 'f'.repeat(32), release_id: 1, files: 2, created_at: hourAgo })
+    // Never run: everything.
+    assert.equal((await new Par2Merger().round()).sets, 1)
+    const saved = await db.from('worker_cursors').where('name', 'merger').firstOrFail()
+    assert.isAbove(new Date(saved.at).getTime(), hourAgo.getTime())
+    // A new process (a deploy) reads where the last round started: the set an hour old is behind it.
+    assert.equal((await new Par2Merger().round()).sets, 0)
+    await db.from('worker_cursors').where('name', 'merger').update({ at: new Date(hourAgo.getTime() - 60_000) })
+    assert.equal((await new Par2Merger().round()).sets, 1)
+  })
+
   test('a set held by two of the releases merged is held once by the target', async ({ assert }) => {
     const at = new Date('2022-07-08T03:46:00Z')
     const ids: number[] = []