All Linode creates fire simultaneously via async/poll:0 loop instead of
serial include_tasks. One shared root pass + SSH key generated before
the loop eliminates per-node credential races. async_status collects
all create confirmations before add_host. Play 2 runs with strategy:free
and -f 50 so all nodes configure, scan, and collect results concurrently.
Per-node serial provision file retired — logic is now inline.
n0mad1k