fix: retire orphaned containers when scaling down

When scaling a process type to a smaller count, the indices above the
new count had their `CONTAINER.<proctype>.<idx>` state files deleted but
the underlying Docker containers were never registered for retirement,
so they remained running indefinitely. The cleanup block now reads each
orphaned state file and registers its container id with the existing
`scheduler-register-retired` trigger before the file is removed.

tests/unit/scheduler-docker-local.bats

@@ -175,3 +175,47 @@ teardown() {
   assert_output_contains "Deploys may fail when publishing ports and scaling to multiple containers" 0
   assert_output_contains "Deploys may fail when publishing ports and enabling zero downtime" 0
 }
+
+@test "(scheduler-docker-local) scale down retires orphaned containers" {
+  run create_app
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "dokku checks:set $TEST_APP wait-to-retire 1"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run deploy_app
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "dokku ps:scale $TEST_APP web=2"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "docker ps --filter label=com.dokku.app-name=$TEST_APP --filter label=com.dokku.process-type=web --format '{{.Names}}' | wc -l"
+  echo "output: $output"
+  echo "status: $status"
+  assert_output "2"
+
+  run /bin/bash -c "dokku ps:scale $TEST_APP web=1"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  sleep 2
+
+  run /bin/bash -c "dokku ps:retire"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "docker ps --filter label=com.dokku.app-name=$TEST_APP --filter label=com.dokku.process-type=web --format '{{.Names}}'"
+  echo "output: $output"
+  echo "status: $status"
+  assert_output "$TEST_APP.web.1"
+}