Seed: finished ranges marked done; relay XOVER timeout 10 minutes

- A range reported to its end but not finished (its node went away at
  the very end) was leased again with start past end; nodes asked for
  "from 49208000000 to 49207999999", got 400, and the range failed after
  five leases. The orchestrator now marks such ranges done before
  leasing, and runRange reports them done without fetching.
- Some old ranges come so slowly that one XOVER of 20k headers takes over
  two minutes: five ranges failed on "NNTP reply timed out". The relay
  pool's timeout is SEED_NNTP_TIMEOUT_MS (default 10 minutes, the node's
  HTTP timeout).

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

tests/unit/aggregate.spec.ts

@@ -37,3 +37,20 @@ test.group('aggregate / FileAggregator', () => {
     assert.equal(aggregator.openFiles, 0)
   })
 })
+
+test.group('seed / runRange', () => {
+  test('a range already past its end only reports that it is done', async ({ assert }) => {
+    const { runRange } = await import('#lib/seed/runner')
+    const batches: any[] = []
+    await runRange({
+      client: { group: async () => assert.fail('no GROUP'), xover: async () => assert.fail('no XOVER') },
+      group: 'a.b.test',
+      start: 101,
+      end: 100,
+      sink: async (batch) => {
+        batches.push(batch)
+      },
+    })
+    assert.deepEqual(batches.map((b) => [b.next, b.headers, b.files.length]), [[101, 0, 0]])
+  })
+})